Superconducting tunable-diaphragm transducer for sensitive acceleration measurements

Journal Article · Mon Mar 01 04:00:00 EST 1976 · J. Appl. Phys., v. 47, no. 3, pp. 1168-1178

DOI:https://doi.org/10.1063/1.322699· OSTI ID:4026633

Paik, H J

A very sensitive resonant superconducting accelerometer was developed as a component of a cryogenic gravitational-radiation detector. The device consists of a superconducting test mass and superconducting coils carrying a persistent current. The displacement of the test mass modulates the inductances of the coils and generates an ac magnetic field which is detected by a Josephson- junction magnetometer. The restoring force provided by the magnetic field is used to tune the resonant frequency of the transducer. The expected sensitivity of the system is better than 10$sup -12$g/subE//Hz$sup 1$$/$$sup 2$ (g/subE/=9.8 m/ s$sup 2$) when used to detect accelerations at frequencies lower than 50 Hz. The system has been thoroughly tested and is being used to detect small accelerations of a gravitational-wave antenna caused by the Brownian motion and other external disturbances. When used as a resonant displacement sensor in a gravitational- wave detector cooled to 3 mK, this transducer is capable of converting a displacement of 4x10$sup -20$ m at 1 kHz into an electrical signal detectable with unity signal-to-noise ratio for 1-Hz bandwidth. The gravitational-radiation- flux sensitivity implied by this is 0.1 erg/cm$sup 2$ Hz. This will make not only the observation of expected galactic events possible, but will allow one to extend the scope of observation beyond the Milky Way. The system can be modified to make a sensitive gravity gradiometer. The device in various applications is discussed and the theory of transducer energy coupling, frequency tuning, and parameter optimization is presented. Some experimental results confirming the theory are reported. Included are data showing the temperature dependence of the Q of a niobium diaphragm and the measurement of the low-frequency background acceleration of a magnetically levitated gravitational-wave antenna. (AIP)

• Research Organization: Department of Physics, Stanford University, Stanford, California 94305
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-025853
• OSTI ID: 4026633
• Journal Information: J. Appl. Phys., v. 47, no. 3, pp. 1168-1178, Journal Name: J. Appl. Phys., v. 47, no. 3, pp. 1168-1178; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

*GRAVITATIONAL WAVE DETECTORS-- JOSEPHSON JUNCTIONS
*TRANSDUCERS-- JOSEPHSON JUNCTIONS
420201* --Engineering--Facilities & Equipment--Cryogenic & Superconducting Equipment & Devices
ACCELERATION
ANTENNAS
CRYOGENICS
GRAVITATIONAL RADIATION
GRAVITATIONAL WAVES
MAGNETOMETERS
MEASURING INSTRUMENTS
N42220* --Engineering--Facilities & Equipment--Cryogenic & Superconducting Equipment & Devices
OPERATION
SENSITIVITY