65,492 research outputs found
Potential mechanical loss mechanisms in bulk materials for future gravitational wave detectors
Low mechanical loss materials are needed to further decrease thermal noise in
upcoming gravitational wave detectors. We present an analysis of the
contribution of Akhieser and thermoelastic damping on the experimental results
of resonant mechanical loss measurements. The combination of both processes
allows the fit of the experimental data of quartz in the low temperature region
(10 K to 25 K). A fully anisotropic numerical calculation over a wide
temperature range (10 K to 300 K) reveals, that thermoelastic damping is not a
dominant noise source in bulk silicon samples. The anisotropic numerical
calculation is sucessfully applied to the estimate of thermoelastic noise of an
advanced LIGO sized silicon test mass.Comment: 7 pages, 3 figures, submitted to Journal of Physics: Conference
Series (AMALDI8
Anisotropic Stark Effect and Electric-Field Noise Suppression for Phosphorus Donor Qubits in Silicon
We report the use of novel, capacitively terminated coplanar waveguide (CPW)
resonators to measure the quadratic Stark shift of phosphorus donor qubits in
Si. We confirm that valley repopulation leads to an anisotropic spin-orbit
Stark shift depending on electric and magnetic field orientations relative to
the Si crystal. By measuring the linear Stark effect, we estimate the effective
electric field due to strain in our samples. We show that in the presence of
this strain, electric-field sources of decoherence can be non-negligible. Using
our measured values for the Stark shift, we predict magnetic fields for which
the spin-orbit Stark effect cancels the hyperfine Stark effect, suppressing
decoherence from electric-field noise. We discuss the limitations of these
noise-suppression points due to random distributions of strain and propose a
method for overcoming them
Thermal noise in interferometric gravitational wave detectors due to dielectric optical coatings
We report on thermal noise from the internal friction of dielectric coatings
made from alternating layers of Ta2O5 and SiO2 deposited on fused silica
substrates. We present calculations of the thermal noise in gravitational wave
interferometers due to optical coatings, when the material properties of the
coating are different from those of the substrate and the mechanical loss angle
in the coating is anisotropic. The loss angle in the coatings for strains
parallel to the substrate surface was determined from ringdown experiments. We
measured the mechanical quality factor of three fused silica samples with
coatings deposited on them. The loss angle of the coating material for strains
parallel to the coated surface was found to be (4.2 +- 0.3)*10^(-4) for
coatings deposited on commercially polished slides and (1.0 +- 0.3)*10^{-4} for
a coating deposited on a superpolished disk. Using these numbers, we estimate
the effect of coatings on thermal noise in the initial LIGO and advanced LIGO
interferometers. We also find that the corresponding prediction for thermal
noise in the 40 m LIGO prototype at Caltech is consistent with the noise data.
These results are complemented by results for a different type of coating,
presented in a companion paper.Comment: Submitted to LSC (internal) review Sept. 20, 2001. To be submitted to
Phys. Lett.
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