He-II filled marionette suspension for the cryogenic payload of the ET-LF interferometer

The low-frequency interferometer in the Einstein Telescope (ET-LF) shall be operated at test mass temperatures of 10 to 20 K. Motivated by the potential of using superfluid helium (He-II) for cooling the test masses due to its exceptional heat transport properties and presumably low dissipative behaviour, we present the concept of integrating a double-walled He-II filled marionette suspension in the payload design. During the cool-down process, supercritical helium (He-I) at adjustable temperature flows in counter-flow through the double-walled suspension in order to cool the marionette. In steady-state operation, the suspension is filled with liquid He-II at rest, providing ultra-low noise cooling at 2 K via steady-state heat conduction. Considering the crucial role of the payload suspensions on the ET-LF sensitivity, we present the results of a thermal and mechanical feasibility analysis with particular focus on suspension thermal noise

Concepts for the Integration of Renewable Synthetic Fuels into an Existing Refinery Structure [Konzepte zur Integration erneuerbarer synthetischer Kraftstoffe in einen bestehenden Raffinerieverbund]

Die Bewältigung der globalen Klimakrise fordert neben neuen Ansätzen auch Strategien zur Transformation fossiler Technologien im Sinne der Nachhaltigkeit. Im Verkehrssektor ist der zukünftige nicht-fossile Energiemix weiterhin nur schwer absehbar. Neben der sicheren Elektrifizierung des Nahverkehrs ist es unumgänglich für die Übergangsphase sowie auch für den Transportsektor Alternativen aufzuzeigen. In der vorliegenden Studie wird die Integration erneuerbarer Benzin- und Dieselkraftstoffe nach der Biomass-to-Liquid- und Power-to-Liquid-Route in eine Raffinerie diskutiert und basierend auf Bilanzen bewertet

Test facility for experimental investigations of the He-II based ET-LF payload cooling concept

The Einstein Telescope (ET) is a third generation gravitational wave detector, combining a low-frequency (LF) and a high-frequency (HF) laser interferometer. Cryogenic operation of ET-LF in the temperature range of 10-20 K is essential to suppress the suspension thermal noise (STN), which dominates the detection sensitivity at frequencies below 10 Hz. The minimization of the STN requires suspension materials with high thermal conductivity and low mechanical dissipation at cryogenic temperatures. Motivated by the exceptional heat conductivity of static He-II and a presumably low dissipation, a new marionette suspension design with a He-II filled titanium tube has been proposed and, theoretically, shown to meet the ET-D sensitivity requirements. The concept includes open fundamental questions that can only be addressed by measurements of the mechanical Q-factor, providing crucial insights in the dissipative behaviour of such a system. Hence, an experimental setup for cryogenic Q-factor measurements is being planned. The scope of experiments and a first conceptual design are being presented here. Beside the Q-factor measurements, a main focus of this facility is given to R&D on the integration of the He-II system and the mechanical interface to the payload in view of noise isolation

Conceptual cryostat design for cryogenic suspension studies for the Einstein Telescope

The Einstein Telescope (ET) is a third generation gravitational wave detector, combining a low-frequency (LF) and a high-frequency (HF) laser interferometer. Cryogenic operation of ET-LF in the temperature range of 10K to 20K is essential to suppress the suspension thermal noise, which dominates the detection sensitivity at frequencies below 10 Hz. This requires suspension materials with high thermal conductivity and low mechanical dissipation at cryogenic temperatures. Two possible suspension concepts are currently considered, using either monocrystalline suspension fibers made of silicon or sapphire, or titanium suspension tubes filled with static He-II. The dissipative behavior of these suspensions is characterized by the mechanical Q-factor. It can be measured by the ring-down method, exciting the suspensions to resonance vibrations on the nanometer scale and analyzing the decay time. For this purpose, a new cryogenic test facility is being planned, allowing the investigation of cryogenic payload suspensions for third-generation gravitational wave detectors. The test cryostat is equipped with a cryocooler and enables real-size studies with various suspension materials and geometries. The future integration of He-II is foreseen to enable He-II filled suspension studies. We describe the scope of experiments and the conceptual design of the test cryostat

Cryogenic payloads for the Einstein Telescope -- Baseline design with heat extraction, suspension thermal noise modelling and sensitivity analyses

The Einstein Telescope (ET) is a third generation gravitational wave detector that includes a room-temperature high-frequency (ET-HF) and a cryogenic low-frequency laser interferometer (ET-LF). The cryogenic ET-LF is crucial for exploiting the full scientific potential of ET. We present a new baseline design for the cryogenic payload that is thermally and mechanically consistent and compatible with the design sensitivity curve of ET. The design includes two options for the heat extraction from the marionette, based on a monocrystalline high-conductivity marionette suspension fiber and a thin-wall titanium tube filled with static He-II, respectively. Following a detailed description of the design options and the suspension thermal noise (STN) modelling, we present the sensitivity curves of the two baseline designs, discuss the influence of various design parameters on the sensitivity of ET-LF and conclude with an outlook to future R&D activities.Comment: 20 pages, Article to be published/submitted in Physical Review D - Journa

Science with the Einstein Telescope: a comparison of different designs

The Einstein Telescope (ET), the European project for a third-generation gravitational-wave detector, has a reference configuration based on a triangular shape consisting of three nested detectors with 10 km arms, where in each arm there is a `xylophone' configuration made of an interferometer tuned toward high frequencies, and an interferometer tuned toward low frequencies and working at cryogenic temperature. Here, we examine the scientific perspectives under possible variations of this reference design. We perform a detailed evaluation of the science case for a single triangular geometry observatory, and we compare it with the results obtained for a network of two L-shaped detectors (either parallel or misaligned) located in Europe, considering different choices of arm-length for both the triangle and the 2L geometries. We also study how the science output changes in the absence of the low-frequency instrument, both for the triangle and the 2L configurations. We examine a broad class of simple `metrics' that quantify the science output, related to compact binary coalescences, multi-messenger astronomy and stochastic backgrounds, and we then examine the impact of different detector designs on a more specific set of scientific objectives.Comment: 197 pages, 72 figure