Towards a Carbon Nanotube Ionization Source for Planetary Atmosphere Exploration

Abstract:

The characterization of planetary exospheres today, relies on the development of a highly efficient ionization source, due to the scant neutral molecules ( n < ⁸ cm^-3 ) present in diffuse, yet gravitationally-bound planetary coronae. These tenuous atmospheres provide insight on to physical processes known to occur such as: space weathering, magneto-atmosphere interactions, as well as atmospheric escape processes, all of which are being heavily investigated via current 3D Monte Carlo simulations (Turc et al. 2014, Leblanc et al. 2015). Neutral detection strongly depends on electron-impact ionization which via conventional cathode-sources, such as thermal filaments (heated to 2000K), can only produce the target ionization essential for energy-measurements with large power consumption. Carbon nanotubes (CNTs) however, are ideal low-power and cold sources when subject to moderate electric fields (E ~ 1 M V/m). We present our current device, a small CNT chip, of emission area 15 mm² which emits field electrons, that pass through an anode grid and subsequent electrostatic analyzer.