Gravitational-wave astronomy is a completely new way to observe the universe. The breakthroughs made by the National Science Foundation's Advanced LIGO, and its partner observatory Advanced Virgo,1,2 are only the beginning of our exploration of the gravitational-wave sky.3-7 This white paper describes the research and development that will be needed over the next decade to realize “Cosmic Explorer,” the U.S. component of a future third-generation detector network.8 Cosmic Explorer, together with a network of planned and proposed observatories spanning the gravitational-wave spectrum, including LISA9,10 and the Einstein Telescope,11 will be able to determine the nature of the densest matter in the universe; reveal the universe's binary black hole population throughout cosmic time; provide an independent probe of the history of the expanding universe; explore warped spacetime with unprecedented fidelity; and expand our knowledge of how massive stars live, die, and create the matter we see today. This white paper presents a technology development program that will lead to a two-stage plan for Cosmic Explorer, similar to the path successfully followed by the National Science Foundation's LIGO. The first stage (CE1) scales up Advanced LIGO technologies to create an L-shaped interferometric detector with arms that are closer to the wavelength of the gravitational waves targeted by ground-based detectors. A facility with 40 km long arms is the baseline for achieving Cosmic Explorer's science goals. The second stage (CE2) upgrades the 40 km detector's core optics using cryogenic technologies and new mirror substrates to realize a full order of magnitude sensitivity improvement beyond Advanced LIGO.12 With its spectacular sensitivity, Cosmic Explorer will see gravitational-wave sources across the history of the universe. Sources that are barely detectable by Advanced LIGO will be resolved with incredible precision. The explosion in the number of detected sources - up to millions per year - and the fidelity of observations will have wide-ranging impact in physics and astronomy. By peering deep into the gravitational-wave sky, Cosmic Explorer will present a unique opportunity for new and unexpected discoveries. Operating as part of a world-wide network with the Einstein Telescope,11 or other possible detectors, Cosmic Explorer will be able to precisely localize sources on the sky,13,14 coupling gravitational-wave astronomy to electromagnetic and particle astronomy. After a review of Cosmic Explorer's scientific potential (§2) and an overview of its design (§3), we outline the engineering study that must be completed in order to design and construct Cosmic Explorer (§4.1). This includes designing a vacuum system for two 40 km beam tubes and developing the civil engineering program needed to prepare the facility site. We then describe a program of laboratory research and prototyping to evolve existing LIGO-class detector components and concepts to those needed for Cosmic Explorer (§4.2). We discuss a program of international collaboration to coordinate the construction and operation of a unified third-generation network of gravitational-wave detectors (§5). Finally, we summarize the schedule and cost of these activities (§6). The new technologies needed to realize Cosmic Explorer (including cost-effective long ultrahigh-vacuum systems, civil engineering studies, new optical materials, and cryogenics) will require a substantial investment in research and design, large-scale prototyping, and tabletop research. A three-year “Horizon Study,” funded by the National Science Foundation (PHY-1836814), is underway to lay the groundwork for the activities described in this white paper. However, this is only the first step: further investment at a level of $65.7M (cost category: medium scale ground-based) early in the coming decade will be needed to ensure that CE1 can begin observing in the 2030s, with CE2 to be operational in the 2040s.
|Original language||English (US)|
|State||Published - Jul 10 2019|
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