Charging of free-falling test masses in orbit due to cosmic rays: results from LISA Pathfinder

Abstract

A comprehensive summary of the measurements made to characterize test mass charging due to the space environment during the LISA Pathfinder mission is presented. Measurements of the residual charge of the test mass after release by the grabbing and positioning mechanism, show that the initial charge of the test masses was negative after all releases, leaving the test mass with a potential in the range $-12$ mV to $-512$ mV. Variations in the neutral test mass charging rate between $21.7$ e s${}^{-1}$ and $30.7$ e s${}^{-1}$ were observed over the course of the 17-month science operations produced by cosmic ray flux changes including a Forbush decrease associated with a small solar energetic particle event. A dependence of the cosmic ray charging rate on the test mass potential between $-30.2$ e s${}^{-1}$ V${}^{-1}$ and $-40.3$ e s${}^{-1}$ V${}^{-1}$ was observed and this is attributed to a contribution to charging from low-energy electrons emitted from the gold surfaces of the gravitational reference sensor. Data from the on-board particle detector show a reliable correlation with the charging rate and with other environmental monitors of the cosmic ray flux. This correlation is exploited to extrapolate test mass charging rates to a 20-year period giving useful insight into the expected range of charging rate that may be observed in the LISA mission.

17 pages, 10 figures

References in corpus (7)

• Laser Interferometer Space Antenna
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• Charge Induced Acceleration Noise in the LISA Gravitational Reference Sensor
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• Low-energy electromagnetic processes affecting free-falling test-mass charging for LISA and future space interferometers
• Simulating the charging of isolated free-falling masses from TeV to eV energies: detailed comparison with LISA Pathfinder results

Cited by in corpus (3)

• In-depth analysis of LISA Pathfinder performance results: Time evolution, noise projection, physical models, and implications for LISA
• Riding the dark matter wave: Novel limits on general dark photons from LISA Pathfinder
• LISA test-mass charging. Particle flux modeling, Monte Carlo simulations and induced effects on the sensitivity of the observatory