Particle scattering off surfaces: Application in space science

Abstract

In many applications of remote sensing of plasma populations in space science a high detection efficiency of energetic neutral atoms (ENAs) is necessary because the sources of these ENAs are very faint. In the recent years surface science processes occurring during particle scattering off specialized surfaces have been successfully used to detect these ENAs with high efficiency. The relevant processes are kinetic secondary electron emission and surface ionization. When secondary electron emission is used an ENA hits a so-called start surface where it releases a secondary electron, which initiates the measurement sequence. Being scattered off the start surface, the ENA continues its flight until it is absorbed at the stop detector. The time difference between the release of the secondary electron and the detection of the particle at the stop detector is measured and with the path length the velocity of the particle is obtained. Surface ionization, i.e., the formation of negative ions, is the well-known charge transfer process where an atom receives an electron from the scattering surface during the scattering process. In modern space science applications mostly insulating surfaces are used as conversion surfaces since these do not need any preparation in space to be operable and at the same time have very stable performance over years. In this paper we will show the current status of surface-science-based detection technology that is used in present space missions of the European Space Agency (ESA) and the U.S. American space agency (NASA) © 2006 The Surface Science Society of Japan.