In-situ measurement techniques for space plasmas based on floating-mode avalanche photodiode and electrostatic energy-per-charge analyzer

New instrumental developments based on a floating-mode avalanche photodiode (APD) combined with an electrostatic energy-per -charge analyzer were conducted for comprehensive and accurate plasma measurements in wide energy ranges in future space plasma explorations. The advantages of APD, namely, rough energy analysis capability, low dark count, compact dimension, and lightweight, are promising as an advanced in-situ measurement technique. We conducted several types of electron/ion beamline experiments under different floating voltage conditions in order to investigate the properties of particle detections and energy analyses using the floating/ normal-mode APD combined with/without the electrostatic energy-per-charge analyzer. The electron/ion post-acceleration associated with the operation of APD in floating mode reduces the lowermost energies detectable by APD. Applying a high voltage of similar to +/- 5 kV to electrostatically float APD in the combination with an electrostatic analyzer, we can attain wide energy coverages (similar to eV - 100's of keV for electrons, similar to 5 keV/q - 100's of keV/q for ions) with proper energy resolutions, noise reduction due to double energy discrimination, and ion mass discrimination capability particularly to distinguish energetic He2+ components of solar wind origin. This technique would also be useful to distinguish the terrestrial-origin O+ from H+ in energies of > a few tens of keV if the ions outflowing from the Earth's upper atmosphere significantly affect the plasma population after some energization processes in the magnetosphere. When these advanced in-situ measurement techniques are employed in future exploration missions, wide-energy/angular distributions of both electrons and ions in space could be captured simultaneously by a single sensor head with triple-dome structure on spin -stabilized satellite. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.