STROFIO (STart from a ROtating Field mass spectrOmeter)

STROFIO is a highly sensitive neutral mass spectrometer designed to characterise the chemical composition of Mercury’s exosphere. It utilises a continuous time-of-flight (TOF) technique to determine the mass-to-charge (m/q) ratio of neutral particles entering its aperture. Strofio has a sensitivity of 0.14 counts/s at a density of 1 particle/cm3 and achieves a mass resolution (m/∆m) of 60 at mass peak 18 (H2O).

STROFIO Flight Model

STROFIO technological highlights

Neutral particles enter the instrument through one of two apertures, where they are ionised via electron-impact ionisation. The resulting ions are then guided and accelerated into the detector region by an array of programmable electrodes. Upon reaching the detector, the ions encounter a rotating electric field that applies a Coulomb force, bending their trajectories. This bend occurs in a specific plane, marking their start time. The ions traverse the remainder of the detector region until they impact a microchannel plate (MCP) detector, which records both their position and stop time. The rotating electric field operates continuously, ensuring a 100% duty cycle for the detection system.

STROFIO Performance table