ONGOING DETECTOR CHARACTERIZATION PROJECTS
This page provides an insight into projects that various EGRG members work on.
All projects are carried out under the supervision of one, two, or more working groups of the LIGO Scientific Collaboration (LSC). Projects must be in line with collaborational activities described in LSC white papers. For an example of such an LSC white paper, click HERE.
Additionally, results of the projects must be reported annually to the LSC, where they undergo a review process carried out by a dedicated LSC committee. The annual review of group activities must be satisfactory in order to have a member group's memorandum of understanding for the following work year signed by LSC representatives.
EGRG has been a member of the LSC since 2007. For an overview of a few selected projects from the past, please click HERE.
Scientific monitoring at the LIGO Livingston site
Raffai, in coordination with the DetChar Working Group
We have participated in the on-site activities at the LIGO Livingston site, by completing the group's duties in science monitoring. The main responsibility of a scientific monitor (or "scimon") is to vouch for data quality being reasonable, as seen from the control room, for gravitational waves discovered during their shifts. They and the operators jointly decide when to start a science segment. Scimons also use the opportunity of being close to the instrument, operators, local commissioners, and control room software tools to investigate and characterize problems happening during the shift (in general with the operator's help), providing clues for commissioners for fixing the problem, and even stopping a science segment if data quality is bad enough. Within one 8 hour shift, scimons need to file reports on detector figures of merits, on their mandatory investigations on the origin of loudest glitches and lock losses during their shift. They also need to participate in triggering follow-up electromagnetic observations after significant detector events, and in creating data quality flags for future search processes.
Peter Raffai in the control room of the LIGO Livingston detector site.
While we were on duty with our scimon shifts, the rare event of a hurricane passing by occured on 9 Nov 2009. The plot shows the coincidentally increased seism registered by LIGO PEM seismometers.
Operating an infrasound monitoring system at the Advanced LIGO detectors
Nagy, Molnár, Fenyvesi, in coordination with the DetChar Working Group
We have developed a routine that includes the following processes needed to develop and maintain an infrasound monitoring system as part of the Advanced LIGO Physical Environmental Monitoring (PEM) system: (a) manufacturing the microphones, (b) calibrating the microphones, (c) comparing the microphones in order to make more accurate simultaneous measurements, and (d) integrating the microphones into a complex physical environment monitoring system, such as the LIGO PEM.
The basic concept of our microphone is quite simple: ambient pressure is measured relative to a pressure reference inside a small volume. The heart of the system is a completely self-designed very sensitive differential pressure sensor with resolution better than 1 mPa. We have developed a calibrating process in order to determine the characteristics and the differential pressure versus the digital output of our microphones. To calibrate each sensor independently, EGRG has built a calibration unit to determine the sensitivity of a sensor. When the sensitivity and the transfer function are determined, we can also cross-calibrate our sensors with each other.
The infrasound monitoring system can be used in studying effects of infrasound on GW detectors, in monitoring infrasound backgrounds at the GW detector sites, and in finding and characterizing the most silent places for GW detectors to be built in the future.
Edit Fenyvesi and David Nagy calibrating infrasound microphones
at the Institute for Nuclear Research (ATOMKI), Debrecen
Analyzing the data of infrasound microphones working in the LIGO PEM system
Edit Fenyvesi, in coordination with the DetChar Working Group
In 2014 EGRG members installed six microphones at LIGO sites. Three microphones were integrated into the LIGO PEM system both at the Hanford and Livingston sites. Since 2014, our microphones are continuously monitoring the on-site acoustic noise backgrounds.
While it helps EGRG members to explore and study the possible infrasound coupling to the gravitational-wave (GW) data channel, our infrasound monitoring system also helps in distinguishing signals of infrasound origin from other sources of data in the LIGO strain output. Veto methods automatically check whether there are noise outliers in the data of the infrasound monitoring system around the time of a GW candidate alert, and create a notice about such coincidences in the LIGO data flow. Notices of this kind are taken into account both in making low-latency decisions on whether to send out an alert to electromagnetic partners interested in making follow-up observations, and later on in the detailed offline analysis of the LIGO strain data.
Beyond operating and maintaining the infrasound monitoring system operating at the LIGO sites, we also carry out detailed analyzes on the data of this system as a part of our work. We compare the average acoustic noise level at each station (i.e. at both end stations, and at the corner station) at Hanford and Livingston. We investigate correlations between the microphone data and data from various other channels, with a special attention given to the LIGO output strain channels. Correlations are currently being studied at various times and for various environmental conditions (decreased or increased noise levels caused by anthropogenic activity, winds, seismic activities, etc.).
We also aim to identify transient events in the infrasound data by using various existing LIGO data analysis techniques. We are searching for events of the greatest energy content detected in a given time interval and try to find correlated events between different stations, and different detector sites. Characterization of the infrasound noise background includes determination of the energy distribution of event tiles during given time periods.
Edit Fenyvesi (ATOMKI, Debrecen) working remotely on analyzing
infrasound data of our microphone system implemented at the two LIGO sites
A spectrogram of the data collected by our microphone at LIGO Hanford, showing a variable frequency signal and its harmonics (possibly due to airplane traffic).
|(c) Eötvös Gravity Research Group 2007|