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Matthew Evans

Publications and source records attributed to Matthew Evans.

At least 37 records · Page 2Linked to original sources
arXiv2022

Next Generation Observatories -- Report from the Dawn VI Workshop; October 5-7 2021

The workshop Dawn VI: Next Generation Observatories took place online over three days, 5-7 October, 2021. More than 200 physicists and astronomers attended to contribute to, and learn from, a discussion of next-generation ground-based gravitational-wave detectors. The program was centered on the next generation of ground-based gravitational-wave observatories and their synergy with the greater landscape of scientific observatories of the 2030s. Cosmic Explorer (CE), a concept developed with US National Science Foundation support, was a particular focus; Einstein Telescope (ET), the European next generation concept, is an important complement and partner in forming a network. The concluding summary of the meeting expressed the sentiment that the observational science accessible to CE and ET, also in combination with data from other non-GW observatories, will stimulate a very broad community of analysts and yield insights which are exciting given the access to GWs from the entire universe. The need, and desire, for closer collaboration between ET and CE was expressed; a three-detector network is optimal for delivering much of the science. The science opportunities afforded by CE and ET are broad and compelling, impacting a wide range of disciplines in physics and high energy astrophysics. There was a consensus that CE is a concept that can deliver the promised science. A strong endorsement of Cosmic Explorer, as described in the CE Horizon Study, is a primary outcome of DAWN VI.

astro-ph.IM↗
arXiv2021

A Horizon Study for Cosmic Explorer: Science, Observatories, and Community

This Horizon Study describes a next-generation ground-based gravitational-wave observatory: Cosmic Explorer. With ten times the sensitivity of Advanced LIGO, Cosmic Explorer will push gravitational-wave astronomy towards the edge of the observable universe ($z \sim 100$). The goals of this Horizon Study are to describe and evaluate design concepts for Cosmic Explorer; to plan for the United States' leadership in gravitational-wave astronomy; and to envisage the role of Cosmic Explorer in the international effort to build a "Third-Generation" (3G) observatory network that will make discoveries transformative across astronomy, physics, and cosmology.

astro-ph.IM↗
arXiv2021

Gravitational-wave physics with Cosmic Explorer: limits to low-frequency sensitivity

Cosmic Explorer (CE) is a next-generation ground-based gravitational-wave observatory concept, envisioned to begin operation in the 2030s, and expected to be capable of observing binary neutron star and black hole mergers back to the time of the first stars. Cosmic Explorer's sensitive band will extend below 10 Hz, where the design is predominantly limited by geophysical, thermal, and quantum noises. In this work, thermal, seismic, gravity-gradient, quantum, residual gas, scattered-light, and servo-control noises are analyzed in order to motivate facility and vacuum system design requirements, potential test mass suspensions, Newtonian noise reduction strategies, improved inertial sensors, and cryogenic control requirements. Our analysis shows that with improved technologies, Cosmic Explorer can deliver a strain sensitivity better than $10^{-23}/\mathrm{Hz}^{1/2}$ down to 5 Hz. Our work refines and extends previous analysis of the Cosmic Explorer concept and outlines the key research areas needed to make this observatory a reality.

gr-qc↗
arXiv2021

Point absorbers in Advanced LIGO

Small, highly absorbing points are randomly present on the surfaces of the main interferometer optics in Advanced LIGO. The resulting nano-meter scale thermo-elastic deformations and substrate lenses from these micron-scale absorbers significantly reduces the sensitivity of the interferometer directly though a reduction in the power-recycling gain and indirect interactions with the feedback control system. We review the expected surface deformation from point absorbers and provide a pedagogical description of the impact on power build-up in second generation gravitational wave detectors (dual-recycled Fabry-Perot Michelson interferometers). This analysis predicts that the power-dependent reduction in interferometer performance will significantly degrade maximum stored power by up to 50% and hence, limit GW sensitivity, but suggests system wide corrections that can be implemented in current and future GW detectors. This is particularly pressing given that future GW detectors call for an order of magnitude more stored power than currently used in Advanced LIGO in Observing Run 3. We briefly review strategies to mitigate the effects of point absorbers in current and future GW wave detectors to maximize the success of these enterprises.

physics.ins-det↗
arXiv2021

Distance measures in gravitational-wave astrophysics and cosmology

We present quantities which characterize the sensitivity of gravitational-wave observatories to sources at cosmological distances. In particular, we introduce and generalize the horizon, range, response, and reach distances. These quantities incorporate a number of important effects, including cosmologically well-defined distances and volumes, cosmological redshift, cosmological time dilation, and rate density evolution. In addition, these quantities incorporate unique aspects of gravitational wave detectors, such as the variable sky sensitivity of the detectors and the scaling of the sensitivity with inverse distance. An online calculator (https://users.rcc.uchicago.edu/~dholz/gwc/) and python notebook (https://github.com/hsinyuc/distancetool) to determine GW distances are available. We provide answers to the question: "How far can gravitational-wave detectors hear?"

astro-ph.CO↗
arXiv2020

Demonstration of an amplitude filter cavity at gravitational-wave frequencies

Quantum vacuum fluctuations fundamentally limit the precision of optical measurements, such as those in gravitational-wave detectors. Injection of conventional squeezed vacuum can be used to reduce quantum noise in the readout quadrature, but this reduction is at the cost of increasing noise in the orthogonal quadrature. For detectors near the limits imposed by quantum radiation pressure noise (QRPN), both quadratures impact the measurement, and the benefits of conventional squeezing are limited. In this paper, we demonstrate the use of a critically-coupled 16m optical cavity to diminish anti-squeezing at frequencies below 90Hz where it exacerbates QRPN, while preserving beneficial squeezing at higher frequencies. This is called an amplitude filter cavity, and it is useful for avoiding degradation of detector sensitivity at low frequencies. The attenuation from the cavity also provides technical advantages such as mitigating backscatter.

astro-ph.IM↗
arXiv2020

Optimal detuning for quantum filter cavities

Vacuum quantum fluctuations impose a fundamental limit on the sensitivity of gravitational-wave interferometers, which rank among the most sensitive precision measurement devices ever built. The injection of conventional squeezed vacuum reduces quantum noise in one quadrature at the expense of increasing noise in the other. While this approach improved the sensitivity of the Advanced LIGO and Advanced Virgo interferometers during their third observing run (O3), future improvements in arm power and squeezing levels will bring radiation pressure noise to the forefront. Installation of a filter cavity for frequency-dependent squeezing provides broadband reduction of quantum noise through the mitigation of this radiation pressure noise, and it is the baseline approach planned for all of the future gravitational-wave detectors currently conceived. The design and operation of a filter cavity requires careful consideration of interferometer optomechanics as well as squeezing degradation processes. In this paper, we perform an in-depth analysis to determine the optimal operating point of a filter cavity. We use our model alongside numerical tools to study the implications for filter cavities to be installed in the upcoming "A+" upgrade of the Advanced LIGO detectors.

astro-ph.IM↗
arXiv2020

Tuning Advanced LIGO to kilohertz signals from neutron-star collisions

Gravitational waves produced at kilohertz frequencies in the aftermath of a neutron star collision can shed light on the behavior of matter at extreme temperatures and densities that are inaccessible to laboratory experiments. Gravitational-wave interferometers are limited by quantum noise at these frequencies but can be tuned via their optical configuration to maximize the probability of post-merger signal detection. We compare two such tuning strategies to turn Advanced LIGO into a post-merger-focused instrument: first, a wideband tuning that enhances the instrument's signal-to-noise ratio 40--80\% broadly above \SI{1}{\kHz} relative to the baseline, with a modest sensitivity penalty at lower frequencies; second, a "detuned" configuration that provides even more enhancement than the wideband tuning, but over only a narrow frequency band and at the expense of substantially worse quantum noise performance elsewhere. With an optimistic accounting for instrument loss and uncertainty in post-merger parameters, the detuned instrument has a ${\lesssim}40\%$ sensitivity improvement compared to the wideband instrument.

astro-ph.IM↗
arXiv2020

Avoiding COVID-19: Aerosol Guidelines

The COVID-19 pandemic has brought into sharp focus the need to understand respiratory virus transmission mechanisms. In preparation for an anticipated influenza pandemic, a substantial body of literature has developed over the last few decades showing that the short-range aerosol route is an important, though often neglected transmission path. We develop a simple mathematical model for COVID-19 transmission via aerosols, apply it to known outbreaks, and present quantitative guidelines for ventilation and occupancy in the workplace.

physics.soc-ph↗
arXiv2019

Searching for Axion Dark Matter with Birefringent Cavities

Axion-like particles are a broad class of dark matter candidates which are expected to behave as a coherent, classical field with a weak coupling to photons. Research into the detectability of these particles with laser interferometers has recently revealed a number of promising experimental designs. Inspired by these ideas, we propose the Axion Detection with Birefringent Cavities (ADBC) experiment, a new axion interferometry concept using a cavity that exhibits birefringence between its two, linearly polarized laser eigenmodes. This experimental concept overcomes several limitations of the designs currently in the literature, and can be practically realized in the form of a simple bowtie cavity with tunable mirror angles. Our design thereby increases the sensitivity to the axion-photon coupling over a wide range of axion masses.

hep-ph↗
arXiv2019

A compact actively damped vibration isolation platform for optical experiments in ultra-high vacuum

We present a tabletop six-axis vibration isolation system, compatible with Ultra-High Vacuum (UHV), which is actively damped and provides 25 dB of isolation at 10 Hz and 65 dB at 100 Hz. While this isolation platform has been primarily designed to support optics in the Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, it is suitable for a variety of applications. The system has been engineered to facilitate the construction and assembly process, while minimizing cost. The platform provides passive isolation for six degrees of freedom using a combination of vertical springs and horizontal pendula. It is instrumented with voice-coil actuators and optical shadow sensors to damp the resonances. All materials are compatible with stringent vacuum requirements. Thanks to its architecture, the system's footprint can be adapted to meet spatial requirements, while maximizing the dimensions of the optical table. Three units are currently operating for LIGO. We present the design of the system, controls principle, and experimental results.

physics.ins-det↗
arXiv2019

The US Program in Ground-Based Gravitational Wave Science: Contribution from the LIGO Laboratory

Recent gravitational-wave observations from the LIGO and Virgo observatories have brought a sense of great excitement to scientists and citizens the world over. Since September 2015,10 binary black hole coalescences and one binary neutron star coalescence have been observed. They have provided remarkable, revolutionary insight into the "gravitational Universe" and have greatly extended the field of multi-messenger astronomy. At present, Advanced LIGO can see binary black hole coalescences out to redshift 0.6 and binary neutron star coalescences to redshift 0.05. This probes only a very small fraction of the volume of the observable Universe. However, current technologies can be extended to construct "$3^\mathrm{rd}$ Generation" (3G) gravitational-wave observatories that would extend our reach to the very edge of the observable Universe. The event rates over such a large volume would be in the hundreds of thousands per year (i.e.tens per hour). Such 3G detectors would have a 10-fold improvement in strain sensitivity over the current generation of instruments, yielding signal-to-noise ratios of 1000 for events like those already seen. Several concepts are being studied for which engineering studies and reliable cost estimates will be developed in the next 5 years.

astro-ph.IM↗
arXiv2019

Quantum limit for laser interferometric gravitational wave detectors from optical dissipation

We derive a quantum limit to the sensitivity of laser interferometric gravitational-wave detectors from optical-loss-induced dissipation, analogous to the sensitivity limit from the mechanical dissipation. It applies universally to different interferometer configurations, and cannot be surpassed unless the optical property is improved. This result provides an answer to the long-standing question of how far we can push the detector sensitivity given the state-of-the-art optics.

quant-ph↗
arXiv2019

Metrics for next-generation gravitational-wave detectors

Gravitational-wave astrophysics has the potential to be transformed by a global network of longer, colder, and thus more sensitive detectors. This network must be constructed to address a wide range of science goals, involving binary coalescence signals as well as signals from other, potentially unknown, sources. It is crucial to understand which network configurations---the number, type, and location of the detectors in the network---can best achieve these goals. In this work we examine a large number of possible three-detector networks, variously composed of Voyager, Einstein Telescope, and Cosmic Explorer detectors, and evaluate their performance against a number of figures of merit meant to capture a variety of future science goals. From this we infer that network performance, including sky localization, is determined most strongly by the type of detectors contained in the network, rather than the location and orientation of the facilities.

astro-ph.IM↗
arXiv2018

Passive optical gyroscope with double homodyne readout

We present a passive, resonant, single-frequency gyroscope design that utilises polarisation modes of an optical cavity to readout rotation and generate a laser frequency discriminant. This design is notable for its simplicity, requiring no modulation electronics or frequency counters. We extract both the cavity length signal and rotation signal from two co-propagating beams with orthogonal polarisations. This readout scheme can be applied to an optical cavity whose polarisation eigen-modes experience different phase shifts such as fibre rings; whispering gallery mode resonators; and folded free-space cavities. We apply this technique to the passive free-space gyroscope and achieve a bias stability of 0.03 degree/h and a sensitivity of $5 \times 10^{-8}$ rad/sqHz above 1 Hz, with a cavity of area 400 cm^2 and finesse of 10^4. Below 1 Hz the sensitivity of the gyroscope is limited by the backscattering in the optical cavity and beam jitter of the laser beam.

physics.optics↗
arXiv2018

Mitigation of the instrumental noise transient in gravitational-wave data surrounding GW170817

In the coming years gravitational-wave detectors will undergo a series of improvements, with an increase in their detection rate by about an order of magnitude. Routine detections of gravitational-wave signals promote novel astrophysical and fundamental theory studies, while simultaneously leading to an increase in the number of detections temporally overlapping with instrumentally- or environmentally-induced transients in the detectors (glitches), often of unknown origin. Indeed, this was the case for the very first detection by the LIGO and Virgo detectors of a gravitational-wave signal consistent with a binary neutron star coalescence, GW170817. A loud glitch in the LIGO-Livingston detector, about one second before the merger, hampered coincident detection (which was initially achieved solely with LIGO-Hanford data). Moreover, accurate source characterization depends on specific assumptions about the behavior of the detector noise that are rendered invalid by the presence of glitches. In this paper, we present the various techniques employed for the initial mitigation of the glitch to perform source characterization of GW170817 and study advantages and disadvantages of each mitigation method. We show that, despite the presence of instrumental noise transients louder than the one affecting GW170817, we are still able to produce unbiased measurements of the intrinsic parameters from simulated injections with properties similar to GW170817.

gr-qc↗
arXiv2018

Prospects for detecting gravitational waves at 5 Hz with ground-based detectors

We propose an upgrade to Advanced LIGO (aLIGO), named LIGO-LF, that focuses on improving the sensitivity in the 5-30 Hz low-frequency band, and we explore the upgrade's astrophysical applications. We present a comprehensive study of the detector's technical noises and show that with technologies currently under development, such as interferometrically sensed seismometers and balanced-homodyne readout, LIGO-LF can reach the fundamental limits set by quantum and thermal noises down to 5 Hz. These technologies are also directly applicable to the future generation of detectors. We go on to consider this upgrade's implications for the astrophysical output of an aLIGO-like detector. A single LIGO-LF can detect mergers of stellar-mass black holes (BHs) out to a redshift of z~6 and would be sensitive to intermediate-mass black holes up to 2000 M_\odot. The detection rate of merging BHs will increase by a factor of 18 compared to aLIGO. Additionally, for a given source the chirp mass and total mass can be constrained 2 times better than aLIGO and the effective spin 3-5 times better than aLIGO. Furthermore, LIGO-LF enables the localization of coalescing binary neutron stars with an uncertainty solid angle 10 times smaller than that of aLIGO at 30 Hz, and 4 times smaller when the entire signal is used. LIGO-LF also significantly enhances the probability of detecting other astrophysical phenomena including the tidal excitation of neutron star r-modes and the gravitational memory effects.

astro-ph.IM↗