Towards a Soundcheck accelerometer: sensor testing at the E-TEST cold platform

The Lunar Gravitational-wave Antenna payload is composed of an array of seismic stations in a permanently shadowed crater. Cryogenic superconductive inertial sensors (CSIS) are deployed in the seismic stations and are aimed to detect the differential between the elastic response of the Moon and the suspended inertial sensor proof-mass motion induced by gravitational waves. First, The status of the sensors, as well as an overview of the additional auxiliary technologies embedded in the payload of the lunar gravitational-wave detection mission are reviewed. Then, the discussion is focused on the inertial sensors. It is composed of a frame and an inertial mass in niobium, assembled in a Watt’s linkage configuration. They work in closed loop, using an interferometric read-out and superconducting actuation. They are required to operate at 4K for superconductive purposes and to be sensitive to 1 fm/sqrt(Hz) from 1 Hz onwards. Such sensitive sensors need a specific test bench to assess their performance on Earth. A first version was developed in the framework of the E-TEST prototype. E-TEST is a prototype suspension of a 45 cm diameter silicon mirror cooled down radiatively to 25 K in a suspended cryostat and is aimed at validating R&D to meet ET’s requirements in the relevant environment. Among the novelties to be tested is the new architecture of the seismic isolation system. CSIS is integrated into ETEST, creating a mutually beneficial arrangement. On the one hand, E-TEST provides an adequate quiet cryogenic environment in which the sensitivity and the sensor can be assessed with a Huddle test, and, on the other hand, the sensors provide data on E-TEST new isolation architecture, by allowing the collaboration to determine the isolation reached at the test mass level. This talk focuses on describing the current status of the development of the CSIS, in its first version with the adaption made for E-TEST, and the future enhancements scheduled to fulfill LGWA goals.