We describe the design of the suspension systems for the major optics for Advanced LIGO, the upgrade to LIGO-the Laser Interferometric Gravitational-Wave Observatory. The design is based on that used ...in GEO600-the German/UK interferometric gravitational wave detector, with further development to meet the more stringent noise requirements for Advanced LIGO. The test mass suspensions consist of a four-stage or quadruple pendulum for enhanced seismic isolation. To minimize suspension thermal noise, the final stage consists of a silica mirror, 40 kg in mass, suspended from another silica mass by four silica fibres welded to silica ears attached to the sides of the masses using hydroxide-catalysis bonding. The design is chosen to achieve a displacement noise level for each of the seismic and thermal noise contributions of 10−19 m/√Hz at 10 Hz, for each test mass. We discuss features of the design which has been developed as a result of experience with prototypes and associated investigations.
Local grape cultivars from different countries of the world are an important part of the gene pool of this culture. Of particular interest are the genotypes of the most ancient regions of ...viticulture. The territories of the subtropical zone of Georgia and the central part of Abkhazia belong to one of the centers of origin of the cultural grapevine. The purpose of the work was to genotype native Abkhazian grape cultivars, to study their genetic diversity based on DNA profiling data and to compare them with the genotypes of local varieties of other viticultural regions. Samples of plants were taken on the territory of the Republic of Abkhazia in private farmsteads and in the collection of the agricultural firm "Vina i Vody Abkhazii" ("Wines and Waters of Abkhazia"). The genotyping of the Abkhazian cultivars Avasirhva, Agbizh, Azhapsh, Azhizhkvakva, Azhikvaca, Atvizh, Atyrkuazh, Achkykazh, Kachich was carried out using 14 DNA markers, 9 of which are standard microsatellite markers recommended for the identification of grape varieties. To improve our knowledge about the sizes of the identified alleles, we used the DNA of grape cultivars with a known allelic composition at the analyzed loci. Statistical analysis of the data showed that the observed heterozygosity for the analyzed loci exceeded expected values, which indicates a genetic polymorphism of the studied sample of varieties. Evaluation of genetic similarity within the analyzed group based on the results of genotyping at 14 loci showed that the cultivars Kachich and Azhapsh differed from the other Abkhazian varieties. The obtained DNA profiles of the Abkhazian cultivars were checked for compliance with DNA-fingerprints of grape varieties in the Vitis International Variety Catalogue. The Georgian varieties Azhizhkvakva and Tsitska turned out to be synonyms according to DNA profiles, two varieties from the Database (Italian Albana bianca and Georgian Ojaleshi) have differences in DNA-fingerprints from the varieties Atyrkuazh and Azhikvatsa only in one allele, respectively. When comparing the identified Abkhazian grape genotypes, their difference from the sample of Dagestan, Don, Greek, Turkish, Italian, Spanish, and French varieties and genetic similarity with the genotypes of Georgian grapes were shown.
This paper describes a system of four novel shadow detectors having, collectively, a displacement sensitivity of (69 ± 13) picometres (rms) / Hz, at 500 Hz, over a measuring span of ±0.1 mm. The ...detectors were designed to monitor the vibrations of the 600 mm long, 400 μm diameter, silica suspension fibres of the mirrors for the Advanced LIGO (Laser Interferometer Gravitational wave Observatory) gravitational wave detectors, at the resonances of the so-called Violin Modes (VM). The VM detection system described here had a target sensitivity of 100 pm (rms)/ Hz at 500 Hz, together with, ultimately, a required detection span of ±0.1 mm about the mean position of each fibre-in order to compensate for potential slow drift over time of fibre position, due to mechanical relaxation. The full sensor system, comprising emitters (sources of illumination) and shadow detectors, therefore met these specifications. Using these sensors, VM resonances having amplitudes of 1.2 nm (rms) were detected in the suspension fibres of an Advanced LIGO dummy test-mass. The VM bandwidth of the sensor, determined by its transimpedance amplifier, was 226 Hz-8.93 kHz at the −3 dB points. This paper focuses mainly on the detector side of the shadow sensors. The emitters are described in an accompanying paper.
The search for gravitational wave signals from astrophysical sources has led to the current work to upgrade the two largest of the long-baseline laser interferometers, the LIGO detectors. The first ...fused silica mirror suspensions for the Advanced LIGO gravitational wave detectors have been installed at the LIGO Hanford and Livingston sites. These quadruple pendulums use synthetic fused silica fibers produced using a CO2 laser pulling machine to reduce thermal noise in the final suspension stage. The suspension thermal noise in Advanced LIGO is predicted to be limited by internal damping in the surface layer of the fibers, damping in the weld regions, and the strength of the fibers. We present here a new method for increasing the fracture strength of fused silica fibers by laser polishing of the stock material from which they are produced. We also show measurements of mechanical loss in laser polished fibers, showing a reduction of 30% in internal damping in the surface layer.
The 40kg test masses of the Advanced LIGO interferometric gravitational wave detector will each be suspended on four fibres fabricated from Heraeus Suprasil synthetic silica glass. The ultimate ...tensile breaking stress and fracturing process of loaded silica fibres was investigated in order to develop the technology required to suspend the test mass in a robust and safe manner. The majority of the fibres in this study were pulled by hand in a H2−O2 flame; for comparison, fibres were also pulled on a CO2 laser machine. Carefully prepared fibres were shown to be pristine, i.e. free of surface cracks. Such fibres exhibited breaking strengths as high as 5−6GPa. To analyse the mechanisms of fracture a high speed photographic setup was developed in addition to the use of a high speed video camera. The pristine fibres break in the zone of maximal stress as expected in the model of flawless fibres. Some fibres break at a lower stress and these fractures occur at the fibre ends. This type of fracture is related to the thermal stress induced by local heating which was used to align the fibre in the test structure. The most likely fracture mechanism is based on a thermo-kinetic approach.
► The ultimate tensile breaking stress of fused silica fibres was investigated. ► A large number of fibres fabricated by two methods can be described as pristine. ► Photographic experiments with stills and high speed video record were carried out. ► Fibre heating performed to correct misalignment could cause strength degradation.
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