[P-CG18] Future missions and instrumentation for space and planetary science

[PCG18-07] Development of an ion energy mass spectrometer with graphene foil for the Comet Interceptor Mission

*Emiko Yoshida¹, Satoshi Kasahara¹, Ryo Tao¹ (1.The University of Tokyo)

Keywords:Comet Interceptor, Ion energy mass spectrometer, Development of measuring instrument

The Comet Interceptor mission, scheduled for launch in 2029, will carry an ion energy mass spectrometer. It will provide information about the material composition of the comet's coma using the Time of Fright (TOF) method, which measures the time each ion species takes to complete a trajectory in the electric field from passing through the foil to the electrode. In the mass spectrometer, ion particles ejected from the comet pass through a foil, emitting secondary electrons that provide the starting signal for TOF. As the particles pass through the foil, there is angular scattering, energy loss and charge exchange of the ion particles due to friction and interaction between the particles and atoms in the foil. Therefore, the foil material is an important factor affecting the sensitivity of the mass spectrometer, and amorphous carbon foil has been used in conventional TOF. In recent years, it has been found that substituting graphene foil can reduce the angular scattering. In this study, we loaded the graphene foil into the ion energy mass spectrometer. In the experiment, we attached both graphene and conventional amorphous carbon foils to the thin films of the breadboard model (BBM) of the mass spectrometer, placed it in a vacuum chamber, and irradiated it with ionised particles such as N2+ and CH4+. Graphene films are difficult to handle because they are extremely thin, with a thickness of several atomic layers. However, in this study, we innovated the conventional process by eliminating processes that could damage the films. And we succeeded in attaching the graphene foils to the thin films at the injection port of the mass spectrometer. The results of the TOF measurements with each material showed that the use of graphene improved the mass resolution. We also found that the graphene foils allowed us to obtain the original information before destruction from molecules(e.g. N2+ and CH4+) to ions with the LEF mode. This could not be measured using amorphous carbon foils. By using this instrument on the mission, we can gain new insights into the transport of organic matter during planet formation