Modeling LISA In-band Test Mass Forces Induced by Eddy Currents @LISAcommunity

Uploaded July 2022 | Updated September 2026, 1 hour ago

The performance of LISA is driven by the read-out noise and the residual acceleration of the Test Masses. Among the sources of acceleration noise, the effect of small-time variations in the magnitude of magnetic dipoles is one of the least studied. In LISA such dipoles would be representative of the sensing and actuation circuitry (100kHz and audio frequencies, respectively) but also of other electronic apparatus on board. An oscillating magnetic dipole induces eddy currents in the Test Mass. These currents combined with the inducing magnetic field generate a net force. Given its quadratic nature in the magnetic field, such a force is made of two components: a harmonic part and a DC part. The DC part can easily translate into in-band noise for LISA when the inducing magnetic dipoles exhibit a time modulation of their amplitude. Unlike other noise sources, the eddy current induced force cannot be easily divided in its independent sources and their frequencies, i.e. superposition principle does not apply. A full electromagnetic model comprehensive of the Test Mass and its closest environment is thus necessary.

The aim of this presentation is to provide the status of the investigation of the noise due to harmonic magnetic dipoles as estimated via dedicated FE numerical analyses.

Authors: Carlo Zanoni, Valerio Ferroni
Presenter: Carlo Zanoni

Modeling LISA In-band Test Mass Forces Induced by Eddy Currents

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