Testing the intrinsic noise of a coilmagnet actuator for cryogenic gravitational wave interferometers

Paolo Falferi (1, 2)

1 IFN - CNR Istituto di Fotonica e Nanotecnologie [Trento]
2 Sezione di Padova

The third generation gravitational wave (GW) interferometers that will operate underground and at cryogenic temperatures will need a complex and sophisticated control system to satisfy the requirements on the alignment and position of its optics and keep the detector at its working point. The force actuators of the control systems of the present interferometers are for the most part coil-magnet actuators. To check the possibility of using these actuators also at low temperature we have tested the magnetization and the magnetization noise of a SmCo magnet at 4.2 K. The magnetization loss, measured with a fluxgate magnetometer, is 7%. The magnetization noise has been measured with a SQUID (Superconducting Quantum Interference Device) magnetometer. The application of dc and ac (0.1 Hz) magnetic fields of amplitude comparable to that needed to produce on the magnet a force large enough for the control system, does not change the measured noise. The equivalent maximum force noise produced by the actuator as a result of the magnetization noise of the magnet has been evaluated. Its effect on the sensitivity of a third generation interferometer (Einstein Telescope) is negligible with respect to the most relevant fundamental noise contributions.

Mots clés: 04.80.Nn; 95.55.Ym; 05.40.Ca; 75.30.Mb; 75.50.Ww

Domaines: Relativité Générale et Cosmologie Quantique [gr-qc]

Paolo Falferi. Testing the intrinsic noise of a coilmagnet actuator for cryogenic gravitational wave interferometers. Classical and Quantum Gravity, 2011, 28 (14), pp.145005. ⟨10.1088/0264-9381/28/14/145005⟩. ⟨hal-00719837⟩