853 research outputs found
The upgrade of GEO600
The German / British gravitational wave detector GEO 600 is in the process of
being upgraded. The upgrading process of GEO 600, called GEO-HF, will
concentrate on the improvement of the sensitivity for high frequency signals
and the demonstration of advanced technologies. In the years 2009 to 2011 the
detector will undergo a series of upgrade steps, which are described in this
paper.Comment: 9 pages, Amaldi 8 conference contributio
Parametric instabilities and their control in advanced interferometer GW detectors
A detailed simulation of Advanced LIGO test mass optical cavities shows that
parametric instabilities will excite acoustic modes in the test masses in the
frequency range 28-35 kHz and 64-72 kHz. Using nominal Advanced LIGO optical
cavity parameters with fused silica test masses, parametric instability excites
7 acoustic modes in each test mass, with parametric gain R up to 7. For the
alternative sapphire test masses only 1 acoustic mode is excited in each test
mass with R ~ 2. Fine tuning of the test mass radii of curvature cause the
instabilities to sweep through various modes with R as high as ~2000. Sapphire
test mass cavities can be tuned to completely eliminate instabilities using
thermal g-factor tuning with negligible degradation of the noise performance.
In the case of fused silica test mass, instabilities can be minimized but not
eliminated.Comment: 5 pages, 4 figure
Cost-benefit analysis for commissioning decisions in GEO600
Gravitational wave interferometers are complex instruments, requiring years
of commissioning to achieve the required sensitivities for the detection of
gravitational waves, of order 10^-21 in dimensionless detector strain, in the
tens of Hz to several kHz frequency band. Investigations carried out by the
GEO600 detector characterisation group have shown that detector
characterisation techniques are useful when planning for commissioning work. At
the time of writing, GEO600 is the only large scale laser interferometer
currently in operation running with a high duty factor, 70%, limited chiefly by
the time spent commissioning the detector. The number of observable
gravitational wave sources scales as the product of the volume of space to
which the detector is sensitive and the observation time, so the goal of
commissioning is to improve the detector sensitivity with the least possible
detector down time. We demonstrate a method for increasing the number of
sources observable by such a detector, by assessing the severity of
non-astrophysical noise contaminations to efficiently guide commissioning. This
method will be particularly useful in the early stages and during the initial
science runs of the aLIGO and adVirgo detectors, as they are brought up to
design performance.Comment: 17 pages, 17 figures, 2 table
DC-readout of a signal-recycled gravitational wave detector
All first-generation large-scale gravitational wave detectors are operated at
the dark fringe and use a heterodyne readout employing radio frequency (RF)
modulation-demodulation techniques. However, the experience in the currently
running interferometers reveals several problems connected with a heterodyne
readout, of which phase noise of the RF modulation is the most serious one. A
homodyne detection scheme (DC-readout), using the highly stabilized and
filtered carrier light as local oscillator for the readout, is considered to be
a favourable alternative. Recently a DC-readout scheme was implemented on the
GEO 600 detector. We describe the results of first measurements and give a
comparison of the performance achieved with homodyne and heterodyne readout.
The implications of the combined use of DC-readout and signal-recycling are
considered.Comment: 11 page
GEO 600 and the GEO-HF upgrade program: successes and challenges
The German-British laser-interferometric gravitational wave detector GEO 600
is in its 14th year of operation since its first lock in 2001. After GEO 600
participated in science runs with other first-generation detectors, a program
known as GEO-HF began in 2009. The goal was to improve the detector sensitivity
at high frequencies, around 1 kHz and above, with technologically advanced yet
minimally invasive upgrades. Simultaneously, the detector would record science
quality data in between commissioning activities. As of early 2014, all of the
planned upgrades have been carried out and sensitivity improvements of up to a
factor of four at the high-frequency end of the observation band have been
achieved. Besides science data collection, an experimental program is ongoing
with the goal to further improve the sensitivity and evaluate future detector
technologies. We summarize the results of the GEO-HF program to date and
discuss its successes and challenges
Control and automatic alignment of the output mode cleaner of GEO 600
The implementation of a mode cleaner at the output port of the GEO 600 gravitational wave detector will be part of the upcoming transition from GEO 600 to GEO-HF. Part of the transition will be the move from a heterodyne readout to a DC readout scheme. DC readout performance will be limited by higher order optical modes and control sidebands present at the output port. For optimum performance of DC readout an output mode cleaner (OMC) will clean the output beam of these contributions. Inclusion of an OMC will introduce new noise sources whose magnitudes needed to be estimated and for which new control systems will be needed. In this article we set requirements on the performance of these control systems and investigate the simulated performance of different designs.Science and Technology Facilities Council (STFC)BMBFMax Planck Society (MPG)State of Lower Saxony in GermanyEuropean Gravitational Observatory (EGO)DFG/SFB/Transregio
Commissioning of the tuned DC readout at GEO 600
Recent experimental results from GEO600 operating with a DC readout and a tuned signal recycling cavity are reported. Compared to the S5/Astrowatch setup, two major changes in the configuration have been implemented: the control readout to keep the interferometer on the dark fringe is changed from heterodyne to homodyne readout and the signal recycling cavity is shifted from a 550 Hz detuning to a 0 Hz detuning (also called tuned). As preliminary experiments showed, the tuned DC readout sensitivity is similar to the heterodyne one. To take advantage of the new DC readout detection scheme, an Output Mode Cleaner (OMC) has to be installed. The design, building and testing of the GEO OMC, which consists of a 4 mirrors monolithic ring cavity, will also be presented in this article.Science and Technology Facilities Council (STFC)BMBFMax Planck Society (MPG)State of Lower Saxony in GermanyEuropean Gravitational Observatory (EGO)DFG/SFB/Transregio
The upgrade of GEO 600
The German/ British gravitational wave detector GEO 600 is in the process of being upgraded. The upgrading process of GEO 600, called GEO-HF, will concentrate on the improvement of the sensitivity for high frequency signals and the demonstration of advanced technologies. In the years 2009 to 2011 the detector will undergo a series of upgrade steps, which are described in this paper.Science and Technology Facilities Council (STFC)BMBFMax Planck Society (MPG)State of Lower SaxonyDFG/SFB/Transregio
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