Mariner 10 radiation. The plasma experiment's goal was to study the ionized gases (plasma) of the solar wind, the temperature and density of its electrons, and how the planets affected the velocity of the plasma stream. The experiment contained two components, facing in opposite directions. The Scanning Electrostatic Analyzer was aimed toward the Sun, and could detect positive ions and electrons, which were separated by a set of three concentric hemispherical plates. The Scanning Electron Spectrometer was aimed away from the Sun, and detected only electrons, using just one hemispherical plate. The instruments could be rotated about 60 degrees to either side.
Plasma diagnostics Some atoms are excited by collisions within the plasma and emit radiation. This can be used to probe density fluctuations in a turbulent plasma. In very hot plasmas (as in magnetic fusion experiments), light elements are fully ionized and don't emit line radiation. When a beam of neutral atoms is fired into the plasma, electrons from beam atoms are transferred to hot plasma ions, which form hydrogenic ions which promptly emit line radiation. This radiation is analyzed for ion density, temperature, and velocity. If the plasma is not fully ionized but contains ions that fluoresce, laser-induced fluorescence can provide very