033904-4 Lorenzini et al. Rev.Sci.Instrum.84,033904(2013) The bending point was measured as described in Sec.II. In this case,the wire head is directly clamped to the micro- metric translational stage.The measurement is thus referred to the true end of the wire (a quite different arrangement is used for silica wires,for reasons that will be explained in the fol- lowing).The recorded peak to peak amplitude of the swinging motion under the applied rotation of the upper end,as a func- tion of the vertical displacement,is shown in Figure 6.The ex- perimental points have been fitted with a parabolic curve and the position of the minimum of the curve has been obtained. The resulting bending length,referred to the clamped end of the wire,is =6.6+0.1 mm.This value is in agreement within experimental error with the one previously obtained by making use of the definition of. B.Measurement on silica wires The geometry of a typical silica wire produced for the quasi-monolithic assembly in Virgo+is shown in Figure 7. Two silica parts,called cone and anchor,are welded to the ends of the silica bar before the pulling process.5 This particu- lar design choice is explained by the following considerations. A well known problem in handling silica parts is that even a FIG.8.Sketch of the steel cone holder blocking one end of the wire. very soft touch produces a mechanical damaging,a crack,that causes an abrupt decrease in the breaking strength,eventually leading to a suspension failure.Therefore,one has to always avoid any contact with the thin wires.To handle them during the production and measurement process,the wire ends are welded to chunky parts that in turn are placed in dedicated steel clamping structures,as shown in Figure 8 for the silica cone.(The particular shapes of cones and anchors are opti- mized for the integration in the quasi-monolithic assembly.) The difference in profile and clamping parts at the two ends of the wire is reflected by two different values for the bending length,that can be marked as Ac (cone)and A(an- chor).For the sake of this article,we will consider only the measurement of Ac,but the case of the anchor is completely similar.Considering again Figure 8,we notice that hereon the bending length value is referred to the back plane surface of the cone holder. 0,14 0,12 0.1 0.08 0.06 0.04 0.02 y=157420x2-10687x+181,42 3,30E-02 3.34E-02 338E-02 3.42E-02 3,46E02 3,50E-02 Vertical displacement [m] FIG.7.Scheme of a typical silica wire produced to be assembled in the Virgo+quasi-monolithic suspension. FIG.9.Oscillation peak to peak amplitude of the silica wire with respect to the vertical displacement.Experimental points are fitted with a quadratic function.The resulting bending length is =33.90.1 mm. Reuse of AlP Publishing content is subject to the terms at:https://publishing.aip.org/authors/rights-and-permissions.Download to IP:183.195.251.6 On:Fri.22 Apr 2016 00:58:16033904-4 Lorenzini et al. Rev. Sci. Instrum. 84, 033904 (2013) The bending point was measured as described in Sec. II. In this case, the wire head is directly clamped to the micro￾metric translational stage. The measurement is thus referred to the true end of the wire (a quite different arrangement is used for silica wires, for reasons that will be explained in the fol￾lowing). The recorded peak to peak amplitude of the swinging motion under the applied rotation of the upper end, as a func￾tion of the vertical displacement, is shown in Figure 6. The ex￾perimental points have been fitted with a parabolic curve and the position of the minimum of the curve has been obtained. The resulting bending length, referred to the clamped end of the wire, is λ = 6.6 ± 0.1 mm. This value is in agreement within experimental error with the one previously obtained by making use of the definition of λ. B. Measurement on silica wires The geometry of a typical silica wire produced for the quasi-monolithic assembly in Virgo+ is shown in Figure 7. Two silica parts, called cone and anchor, are welded to the ends of the silica bar before the pulling process.5 This particu￾lar design choice is explained by the following considerations. A well known problem in handling silica parts is that even a FIG. 7. Scheme of a typical silica wire produced to be assembled in the Virgo+ quasi-monolithic suspension. FIG. 8. Sketch of the steel cone holder blocking one end of the wire. very soft touch produces a mechanical damaging, a crack, that causes an abrupt decrease in the breaking strength, eventually leading to a suspension failure. Therefore, one has to always avoid any contact with the thin wires. To handle them during the production and measurement process, the wire ends are welded to chunky parts that in turn are placed in dedicated steel clamping structures, as shown in Figure 8 for the silica cone. (The particular shapes of cones and anchors are opti￾mized for the integration in the quasi-monolithic assembly.) The difference in profile and clamping parts at the two ends of the wire is reflected by two different values for the bending length, that can be marked as λC (cone) and λA (an￾chor). For the sake of this article, we will consider only the measurement of λC, but the case of the anchor is completely similar. Considering again Figure 8, we notice that hereon the bending length value is referred to the back plane surface of the cone holder. FIG. 9. Oscillation peak to peak amplitude of the silica wire with respect to the vertical displacement. Experimental points are fitted with a quadratic function. The resulting bending length is λ = 33.9 ± 0.1 mm. Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions. Download to IP: 183.195.251.6 On: Fri, 22 Apr 2016 00:58:16