Simulation of the charging process of the LISA test masses due to solar particles

Abstract

Cosmic-ray and solar particles above 100 MeV penetrate the LISA experiment test masses. Consequently, electric charges accumulating there generate spurious Coulomb forces between the masses and the surrounding electrodes. This process increments the noise level of the experiment. We have estimated the amount of charge deposited per second on the LISA test masses by primary cosmic-ray protons at solar minimum and solar maximum and by solar energetic particle (SEP) events. This simulation has been carried out with the Fluka Monte Carlo program. A simplified geometry for the experiment has been considered. We have found an effective charge rate of 110 e s−1 for primary protons at solar maximum and 150 e s−1 at solar minimum between 0.1 and 1000 GeV. The amount of charge released by a medium intensity gradual event (7 May 1978) varies from 206 e s−1 in the first few minutes to 4575 e s−1 at the peak of the event. At the occurrence of medium or strong solar events, the LISA sensitivity curve at frequencies lower than 3 × 10−4 Hz is dominated by the noise due to the test-mass charging process.

Simulation of ASTROD I test mass charging due to solar energetic particles and interplanetary electrons

“…Particles generated by impulsive events show maximum energies of 50 MeV. Gradual events are associated with shock acceleration in coronal mass ejections (CMEs) and their spectrum can extend up to a few GeV energies (Vocca et al, 2005). In gradual SEP events, protons of energy greater than 100 MeV can penetrate spacecraft walls and payload structure, and penetrate the test mass.…”

Test mass charging simulation of ASTROD I due to solar energetic particles at 0.5 AU

“…Particles generated by impulsive events exhibit maximum energies of 50 MeV, which is not high enough to penetrate the spacecraft shielding. Gradual events are associated with shock acceleration in coronal mass ejections (CMEs) and their particle energy spectrum can extend up to a few GeV [13]. Protons of energy greater than 100 MeV can penetrate spacecraft walls and payload structure and charge the test mass.…”

Bridging the gap between Monte Carlo simulations and measurements of the LISA Pathfinder test-mass charging for LISA

“…Prelaunch Monte Carlo simulations carried out to estimate the net and effective charging (charging noise) of the LPF TMs during the mission operations (Grimani et al 2004;Vocca et al 2004;Grimani et al 2005;Vocca et al 2005;Araújo et al 2005;Wass et al 2005;Grimani et al 2015) were carried out with the FLUKA (Battistoni et al 2014;Böhlen et al 2014) and Geant4 (Agostinelli et al 2003;Allison et al 2006Allison et al , 2016 toolkits by considering the same satellite geometry. These two sets of simulations agreed excellently when the same input particle fluxes were considered.…”