Microchannel Plates (MCP) detectors are frequently used in space instrumentation for detecting a wide range of radiation
and particles. In particular, the capability to detect non-thermal low energy neutral species is crucial for the sensor
ELENA (Emitted Low-Energy Neutral Atoms), part of the package SERENA (Search for Exospheric Refilling and
Emitted Natural Abundances) on board the BepiColombo mission of ESA to Mercury to be launched in 2015. ELENA is
a Time of Flight (TOF) sensor, based on a novel concept using an ultra-sonic oscillating shutter (Start section), which is
operated at frequencies up to 50 kHz; a MCP detector is used as a Stop detector. The scientific objective of ELENA is to
detect energetic neutral atoms in the range 10 eV – 5 keV, within 76° FOV, perpendicular to the S/C orbital plane.
ELENA will monitor the emission of neutral atoms from the whole surface of Mercury thanks to the spacecraft motion.
The major scientific objectives are the interaction between the plasma environment and the planet’s surface, the global
particle loss-rate and the remote sensing of the surface properties. In particular, surface release processes are investigated
by identifying particles released from the surface, via solar wind-induced ion sputtering (< 1eV – < 100 eV) as well as
Hydrogen back-scattered at hundreds eV. MCP absolute detection efficiency for very low energy neutral atoms (E <
30 eV) is a crucial point for this investigation. At the MEFISTO facility of the Physical Institute of the University of
Bern (CH), measurements on three different types of MCP (with and without coating) have been performed providing
the detection efficiencies in the energy range 10eV – 1keV. Outcomes from such measurements are discussed here.