Galactic cosmic rays and solar energetic particles charge gold-platinum, free-falling test masses (TMs) on board interferometers for the detection of gravitational waves in space. The charging process induces spurious forces on the test masses that affect the sensitivity of these instruments mainly below $10^{-3}$ Hz. Geant4 and FLUKA Monte Carlo simulations were carried out to study the TM charging process on board the LISA Pathfinder mission that remained into orbit around the Sun-Earth Lagrange point L1 between 2016 and 2017. While a good agreement was observed between simulations and measurements of the TMs net charging, the shot noise associated with charging fluctuations of both positive and negative particles resulted 3-4 times higher that predicted. The origin of this mismatch was attributed to the propagation of electrons and photons only above 100 eV in the simulations. In this paper, low-energy electromagnetic processes to be included in the future Monte Carlo simulations for LISA and LISA-like space interferometers TM charging are considered. {It is found that electrons and photons below 100 eV give a contribution to the effective charging comparable to that of the whole sample of particles above this energy. In particular, for incident protons ionization contributes twice with respect to low energy kinetic emission and electron backscattering. The other processes are found to play a negligible role. For heavy nuclei only sputtering must be considered.

中文翻译：

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影响 LISA 和未来空间干涉仪自由落体测试质量充电的低能电磁过程

银河宇宙射线和太阳高能粒子在干涉仪上为金铂、自由落体测试质量 (TM) 充电，用于探测太空中的引力波。充电过程会在测试质量上引起寄生力，影响这些仪器的灵敏度主要低于 $10^{-3}$Hz。进行了 Geant4 和 FLUKA Monte Carlo 模拟以研究 LISA 探路者任务上的 TM 充电过程，该任务在 2016 年至 2017 年间保持在围绕太阳-地球拉格朗日点 L1 的轨道上。虽然在模拟和测量之间观察到良好的一致性TMs 净充电，与正负粒子充电波动相关的散粒噪声比预测值高 3-4 倍。这种不匹配的起源归因于模拟中仅高于 100 eV 的电子和光子的传播。在本文中，考虑了将包含在未来 LISA 和类 LISA 空间干涉仪 TM 充电的蒙特卡罗模拟中的低能电磁过程。{发现低于 100 eV 的电子和光子对有效充电的贡献与高于此能量的整个粒子样本的充电相当。特别是，对于入射质子，电离在低能量动能发射和电子背散射方面贡献了两倍。发现其他过程的作用可以忽略不计。对于重核，只需要考虑溅射。低能电磁过程将包含在未来的 LISA 和 LISA 类空间干涉仪 TM 充电的蒙特卡罗模拟中。{发现低于 100 eV 的电子和光子对有效充电的贡献与高于此能量的整个粒子样本的充电相当。特别是，对于入射质子，电离在低能量动能发射和电子背散射方面贡献了两倍。发现其他过程的作用可以忽略不计。对于重核，只需要考虑溅射。低能电磁过程将包含在未来的 LISA 和 LISA 类空间干涉仪 TM 充电的蒙特卡罗模拟中。{发现低于 100 eV 的电子和光子对有效充电的贡献与高于此能量的整个粒子样本的充电相当。特别是，对于入射质子，电离在低能量动能发射和电子背散射方面贡献了两倍。发现其他过程的作用可以忽略不计。对于重核，只需要考虑溅射。对于入射质子，电离在低能量动能发射和电子背散射方面贡献了两倍。发现其他过程的作用可以忽略不计。对于重核，只需要考虑溅射。对于入射质子，电离在低能量动能发射和电子背散射方面贡献了两倍。发现其他过程的作用可以忽略不计。对于重核，只需要考虑溅射。