title: A high precision, compact electromechanical ground rotation sensor.
abstract: We present a mechanical rotation sensor consisting of a balance pivoting on a tungsten carbide knife edge. These sensors are important for precision seismic isolation systems, as employed in land-based gravitational wave interferometers and for the new field of rotational seismology. The position sensor used is an air-core linear variable differential transformer with a demonstrated noise floor of 1 × 10⁻¹¹ m/√Hz. We describe the instrument construction and demonstrate low noise operation with a noise floor upper bound of 5.7 × 10⁻⁹ rad/√Hz at 10 mHz and 6.4 × 10⁻¹⁰ rad/√Hz at 0.1 Hz. The performance of the knife edge hinge is compatible with a behaviorur free of noise from dislocation self-organized criticality.
authors.affiliation: LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena, California 91125, USA.
authors.forename: V
authors.initials: V
authors.lastname: Dergachev
authors.affiliation: LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena, California 91125, USA.
authors.forename: R
authors.initials: R
authors.lastname: DeSalvo
authors.affiliation: Mayfield Senior School, 500 Bellefontaine Street, Pasadena, California 91105, USA.
authors.forename: M
authors.initials: M
authors.lastname: Asadoor
authors.affiliation: Arcadia High School, 180 Campus Drive, Arcadia, California 91007, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bhawal
authors.affiliation: Department of Precision Instrument, Tsinghua University, Beijing 100084, China.
authors.forename: P
authors.initials: P
authors.lastname: Gong
authors.affiliation: California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: C
authors.initials: C
authors.lastname: Kim
authors.affiliation: Department of Computer Science, University of Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Lottarini
authors.affiliation: Sezione INFN Tor Vergata, via della Ricerca Scientifica  1, 00133 Roma, Italy.
authors.forename: Y
authors.initials: Y
authors.lastname: Minenkov
authors.affiliation: School of Physics, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, Western Australia 6009, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Murphy
authors.affiliation: University of California, Los Angeles, 405 Hilgard Ave, Los Angeles, California 90095, USA.
authors.forename: A
authors.initials: A
authors.lastname: O'Toole
authors.affiliation: National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan.
authors.forename: F E
authors.initials: FE
authors.lastname: Peña Arellano
authors.affiliation: California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Rodionov
authors.affiliation: Mayfield Senior School, 500 Bellefontaine Street, Pasadena, California 91105, USA.
authors.forename: M
authors.initials: M
authors.lastname: Shaner
authors.affiliation: Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Sobacchi