Coatings and surface treatments for enhanced performance suspensions for future gravitational wave detectors

R Birney, A V Cumming, P Campsie, D Gibson, G D Hammond, J Hough, I W Martin, S Reid, S Rowan, S Song, C Talbot, D Vine, G Wallace

Research output: Contribution to journalArticle

Abstract

Further improvements in the low frequency sensitivity of gravitational wave detectors are important for increasing the observable population of astrophysical sources, such as intermediate mass compact black hole binary systems. Improvements in the lower stage mirror and suspension systems will set challenging targets for the required thermal noise performance of the cantilever blade springs, which provide vertical softness and, thus, isolation to the mirror suspension stack. This is required due to the coupling between the vertical and horizontal axes due to the curvature of the Earth. This can be achieved through use of high mechanical Q materials, which are compatible with cryogenic cooling, such as crystalline silicon. However, such materials are brittle, posing further challenges for assembly/jointing and, more generally, for long-term robustness. Here, we report on experimental studies of the breaking strength of silicon at room temperature, via both tensile and 4-point flexural testing; and on the effects of various surface treatments and coatings on durability and strength. Single- and multi-layer DLC (diamond-like carbon) coatings, together with magnetron-sputtered silica and thermally-grown silica, are investigated, as are the effects of substrate preparation and argon plasma pre-treatment. Application of single- or multi-layer DLC coatings can significantly improve the failure stress of silicon flexures, in addition to improved robustness for handling (assessed through abrasion tests). Improvements of up to 80% in tensile strength, a twofold increase in flexural strength, in addition to a 6.4 times reduction in the vertical thermal noise contribution of the suspension stack at 10 Hz are reported (compared to current Advanced LIGO design). The use of silicon blade springs would also significantly reduce potential 'crackling noise' associated with the underlying discrete events associated with plastic deformation in loaded flexures.

LanguageEnglish
Article number235012
Number of pages16
JournalClassical and Quantum Gravity
Volume34
Issue number23
DOIs
Publication statusPublished - 15 Nov 2017

Fingerprint

surface treatment
gravitational waves
coatings
flexing
detectors
thermal noise
silicon
blades
diamonds
cryogenic cooling
mirrors
silicon dioxide
brittle materials
LIGO (observatory)
softness
abrasion
carbon
flexural strength
argon plasma
durability

Keywords

  • coatings
  • diamond-like carbon
  • gravitational wave detectors
  • silicon
  • suspensions
  • thermal noise

Cite this

Birney, R ; Cumming, A V ; Campsie, P ; Gibson, D ; Hammond, G D ; Hough, J ; Martin, I W ; Reid, S ; Rowan, S ; Song, S ; Talbot, C ; Vine, D ; Wallace, G. / Coatings and surface treatments for enhanced performance suspensions for future gravitational wave detectors. In: Classical and Quantum Gravity. 2017 ; Vol. 34, No. 23.
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Birney, R, Cumming, AV, Campsie, P, Gibson, D, Hammond, GD, Hough, J, Martin, IW, Reid, S, Rowan, S, Song, S, Talbot, C, Vine, D & Wallace, G 2017, 'Coatings and surface treatments for enhanced performance suspensions for future gravitational wave detectors' Classical and Quantum Gravity, vol. 34, no. 23, 235012. https://doi.org/10.1088/1361-6382/aa9354

Coatings and surface treatments for enhanced performance suspensions for future gravitational wave detectors. / Birney, R; Cumming, A V; Campsie, P; Gibson, D; Hammond, G D; Hough, J; Martin, I W; Reid, S; Rowan, S; Song, S; Talbot, C; Vine, D; Wallace, G.

In: Classical and Quantum Gravity, Vol. 34, No. 23, 235012, 15.11.2017.

Research output: Contribution to journalArticle

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