1,303 research outputs found
Readout and Control of a Power-recycled Interferometric Gravitational-wave Antenna
Interferometric gravitational wave antennas are based on Michelson
interferometers whose sensitivity to small differential length changes has been
enhanced by adding multiple coupled optical resonators. The use of optical
cavities is essential for reaching the required sensitivity, but sets
challenges for the control system which must maintain the cavities near
resonance. The goal for the strain sensitivity of the Laser Interferometer
Gravitational-wave Observatory (LIGO) is 10^-21 rms, integrated over a 100 Hz
bandwidth centered at 150 Hz. We present the major design features of the LIGO
length and frequency sensing and control system which will hold the
differential length to within 5 10^-14 m of the operating point. We also
highlight the restrictions imposed by couplings of noise into the gravitational
wave readout signal and the required immunity against them.Comment: Presentation at ICALEPCS 2001, San Jose, November 2001, (WECT003), 3
page
An all-optical trap for a gram-scale mirror
We report on a stable optical trap suitable for a macroscopic mirror, wherein
the dynamics of the mirror are fully dominated by radiation pressure. The
technique employs two frequency-offset laser fields to simultaneously create a
stiff optical restoring force and a viscous optical damping force. We show how
these forces may be used to optically trap a free mass without introducing
thermal noise; and we demonstrate the technique experimentally with a 1 gram
mirror. The observed optical spring has an inferred Young's modulus of 1.2 TPa,
20% stiffer than diamond. The trap is intrinsically cold and reaches an
effective temperature of 0.8 K, limited by technical noise in our apparatus.Comment: Major revision. Replacement is version that appears in Phy. Rev.
Lett. 98, 150802 (2007
Atmosphere-snow transfer function for H2O2: microphysical considerations
H2O2 analyses of polar ice cores show an increase in concentration from 200 years to the present. In order to quantitatively relate the observed trend in the ice to atmospheric levels, the atmosphere-snow transfer behavior and postdepositional changes must be known. Atmosphere-snow transfer was studied by investigating uptake and release of H2O2 in a series of laboratory column experiments in the temperature range â3°C to â45°C. Experiments consisted of passing H2O2-containing air through a column packed with 200-ÎŒm diameter ice spheres and measuring the change in gas phase H2O2 concentration with time. The uptake of H2O2 was a slow process requiring several hours to reach equilibrium. Uptake involved incorporation of H2O2 into the bulk ice as well as surface accumulation. The amount of H2O2 taken up by the ice was greater at the lower temperatures. The sticking coefficient for H2O2 on ice in the same experiments was estimated to be of the order of 0.02 to 0.5. Release of H2O2 from the ice occurred upon passing H2O2-free air through the packed columns, with the time scale for degassing similar to that for uptake. These results suggest that systematic losses of H2O2 from polar snow could occur under similar conditions, when atmospheric concentrations of H2O2 are low, that is, in the winter
Benefits of Artificially Generated Gravity Gradients for Interferometric Gravitational-Wave Detectors
We present an approach to experimentally evaluate gravity gradient noise, a
potentially limiting noise source in advanced interferometric gravitational
wave (GW) detectors. In addition, the method can be used to provide sub-percent
calibration in phase and amplitude of modern interferometric GW detectors.
Knowledge of calibration to such certainties shall enhance the scientific
output of the instruments in case of an eventual detection of GWs. The method
relies on a rotating symmetrical two-body mass, a Dynamic gravity Field
Generator (DFG). The placement of the DFG in the proximity of one of the
interferometer's suspended test masses generates a change in the local
gravitational field detectable with current interferometric GW detectors.Comment: 16 pages, 4 figure
Performance of a 1200m long suspended Fabry-Perot cavity
Using one arm of the Michelson interferometer and the power recycling mirror
of the interferometric gravitational wave detector GEO600, we created a
Fabry-Perot cavity with a length of 1200 m. The main purpose of this experiment
was to gather first experience with the main optics, its suspensions and the
corresponding control systems. The residual displacement of a main mirror is
about 150 nm rms. By stabilising the length of the 1200 m long cavity to the
pre-stabilised laser beam we achieved an error point frequency noise of 0.1
mHz/sqrt(Hz) at 100 Hz Fourier frequency. In addition we demonstrated the
reliable performance of all included subsystems by several 10-hour-periods of
continuous stable operation. Thus the full frequency stabilisation scheme for
GEO600 was successfully tested.Comment: Amaldi 4 (Perth 2001) conference proceedings, 10 pages, 8 figure
Photon pressure induced test mass deformation in gravitational-wave detectors
A widely used assumption within the gravitational-wave community has so far
been that a test mass acts like a rigid body for frequencies in the detection
band, i.e. for frequencies far below the first internal resonance. In this
article we demonstrate that localized forces, applied for example by a photon
pressure actuator, can result in a non-negligible elastic deformation of the
test masses. For a photon pressure actuator setup used in the gravitational
wave detector GEO600 we measured that this effect modifies the standard
response function by 10% at 1 kHz and about 100% at 2.5 kHz
Status of the joint LIGO--TAMA300 inspiral analysis
We present the status of the joint search for gravitational waves from
inspiraling neutron star binaries in the LIGO Science Run 2 and TAMA300 Data
Taking Run 8 data, which was taken from February 14 to April 14, 2003, by the
LIGO and TAMA collaborations. In this paper we discuss what has been learned
from an analysis of a subset of the data sample reserved as a ``playground''.
We determine the coincidence conditions for parameters such as the coalescence
time and chirp mass by injecting simulated Galactic binary neutron star signals
into the data stream. We select coincidence conditions so as to maximize our
efficiency of detecting simulated signals. We obtain an efficiency for our
coincident search of 78 %, and show that we are missing primarily very distant
signals for TAMA300. We perform a time slide analysis to estimate the
background due to accidental coincidence of noise triggers. We find that the
background triggers have a very different character from the triggers of
simulated signals.Comment: 10 page, 8 figures, accepted for publication in Classical and Quantum
Gravity for the special issue of the GWDAW9 Proceedings ; Corrected typos,
minor change
A blind hierarchical coherent search for gravitational-wave signals from coalescing compact binaries in a network of interferometric detectors
We describe a hierarchical data analysis pipeline for coherently searching
for gravitational wave (GW) signals from non-spinning compact binary
coalescences (CBCs) in the data of multiple earth-based detectors. It assumes
no prior information on the sky position of the source or the time of
occurrence of its transient signals and, hence, is termed "blind". The pipeline
computes the coherent network search statistic that is optimal in stationary,
Gaussian noise, and allows for the computation of a suite of alternative
statistics and signal-based discriminators that can improve its performance in
real data. Unlike the coincident multi-detector search statistics employed so
far, the coherent statistics are different in the sense that they check for the
consistency of the signal amplitudes and phases in the different detectors with
their different orientations and with the signal arrival times in them. The
first stage of the hierarchical pipeline constructs coincidences of triggers
from the multiple interferometers, by requiring their proximity in time and
component masses. The second stage follows up on these coincident triggers by
computing the coherent statistics. The performance of the hierarchical coherent
pipeline on Gaussian data is shown to be better than the pipeline with just the
first (coincidence) stage.Comment: 12 pages, 3 figures, accepted for publication in Classical and
Quantum Gravit
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