Hydroxide catalysis bonding is a joining technique used in the construction of highly stable opto-mechanical systems including quasi-monolithic silica suspensions for first and second generation ...gravitational wave detectors. Future generations of detector are likely to operate at cryogenic temperatures necessitating a change in testmass/suspension material. A promising candidate material is silicon, which requires an oxide surface layer for hydroxide catalysis bonding to be reliable. Here, we present first results showing the influence of the type of oxide layer applied on bond strength, measured at room temperature and 77 K, and identify preferred oxide deposition methods.
Low mechanical loss, high index-of-refraction thin-film coating materials are of particular interest to the gravitational wave detection community, where reduced mirror coating thermal noise in ...gravitational wave detectors is desirable. Current studies are focused on understanding the loss of amorphous metal oxides such as SiO sub(2), Ta sub(2)O sub(5) and HfO sub(2). Here, we report recent measurements of the temperature dependence of the mechanical loss of ion-beam sputtered hafnium dioxide (HfO sub(2)) coatings that have undergone heat treatment. The results indicate that, even when partially crystallized, these coatings have lower loss than amorphous Ta sub(2)O sub(5) films below ~100 K and that their loss exhibits some features which are heat-treatment dependent in the temperature range of ~100?200 K, with higher heat treatment yielding lower mechanical loss. The potential for using silica doping of hafnia coatings to prevent crystallization is discussed.
Current interferometric gravitational wave detectors use the combination of quasi-monochromatic, continuous-wave laser light at 1064 nm and fused silica test masses at room temperature. Detectors of ...the third generation, such as the Einstein-Telescope, will involve a considerable sensitivity increase. The combination of 1550 nm laser radiation and crystalline silicon test masses at low temperatures might be important ingredients in order to achieve the sensitivity goal. Here we compare some properties of the fused silica and silicon test mass materials relevant for decreasing the thermal noise in future detectors as well as the recent technology achievements in the preparation of laser radiation at 1064 nm and 1550 nm relevant for decreasing the quantum noise. We conclude that silicon test masses and 1550 nm laser light have the potential to form the future building blocks of gravitational wave detection.
Scientific objectives of Einstein Telescope Abernathy, M; Ajith, P; Astone, P ...
Classical and quantum gravity,
06/2012, Letnik:
29, Številka:
12
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The advanced interferometer network will herald a new era in observational astronomy. There is a very strong science case to go beyond the advanced detector network and build detectors that operate ...in a frequency range from 1 Hz to 10 kHz, with sensitivity a factor 10 better in amplitude. Such detectors will be able to probe a range of topics in nuclear physics, astronomy, cosmology and fundamental physics, providing insights into many unsolved problems in these areas.
Low temperature superconducting quantum interference devices (LTS SQUIDs) are used to make precision measurements of electromagnetic fields in applications ranging from biomedicine to high energy ...physics. We have previously described an LTS SQUID-based device for nuclear physics which employs the Cryogenic Current Comparator principle (CCC). The CCC consists of a high-performance LTS DC SQUID system, a toroidal pick-up coil, and a meander-shaped superconducting niobium shield. Theoretical investigations show that as external noise decreases, improvements in performance depend on the properties of the ferromagnetic core material embedded in the pick-up coil. Here we present the temperature- and frequency-dependence of several candidate ferromagnetic and nanocrystalline materials. We discuss these results in light of the optimization of the CCC sensor performance.
Grating reflectors are a potential low-noise replacement for amorphous multilayer mirrors. We investigate the influence of polarization and refractive index on Brownian thermal noise of binary ...grating reflectors using Maxwell's stress tensor. Our results demonstrate that the refractive index of the grating material is a critical parameter for thermal noise in these structures. In contrast to multilayer mirrors, a low coating thickness does not necessarily lead to a low thermal noise amplitude for structures with low refractive index. We find that an improved noise performance of grating reflectors requires materials of refractive index ≳2.5. We present a factorized expression for the thermal noise of grating reflectors made of arbitrary materials by simply scaling the noise amplitude with the related material parameters.
•Study on material and polarization dependence of Brownian thermal noise in binary grating reflectors.•Semi-analytic expression applicable for arbitrary material combinations.•To achieve benefit compared to amorphous multilayer mirrors materials with refractive indices of ≥2.5 are required.•Grating reflectors based on metal oxides not suited for substantial noise improvement.
Mechanical spectroscopy gives information on the structure of solids and their relaxation mechanisms through the measurements of the elastic constants and the mechanical loss angle of materials. One ...common way to estimate these quantities is the resonant method where the frequency and the characteristic decay time of oscillations are measured. Since many solid materials can be easily found in the shape of thin disc we have investigated the mechanical loss of these resonators and we have found experimentally that the loss angle dependence on the mode is not trivial but rather follow a distribution of modes into families. We give a model that is able to justify the existence of these families and to predict the level of losses in silicon, silica and brass discs. The model considers the thermoelastic effect and the excess damping caused by the condition of the disc edge. The results of this research are relevant to the research on thin films that are deposited on thin discs like the optical coatings used on the mirrors for the gravitational wave detectors.
•It provides the first experimental evidence and justification of mode families in loss measurements in discs.•A simple and reliable model of thermoelastic loss in thin discs is provided.•A method of calculation of thermoelastic loss in thick cylinder and non-isotropic materials is provided.•Total loss expression is provided in the most general case of heterogeneous systems with multiple loss mechanisms.
Today’s laser interferometric gravitational wave detectors are sensitivity limited by thermal noise of the optical components within the detection band of about 0.1–1
kHz. Cooling down these parts to ...cryogenic temperatures is a promising technique to increase the sensitivity of the gravitational wave detectors by at least one to two orders of magnitudes. Cooling substantially increases the material Q-factor contributing to reduced thermal noise. This article describes a new cryogenic apparatus which allows the measurement of the mechanical Q-factor – as a measure of internal losses – in a temperature range from 5
K up to 300
K. The requirements for cryogenic Q-factor measurements and their realization are shown. The measuring technique as well as the key parameters are discussed. Exemplary, measurements on crystalline quartz and silicon (1
0
0) are given to characterize the setup.
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