A space-borne analyser for three-dimensional measurements of the velocity distribution

A new type of plasma analyser, capable of covering the three-dimensional energy distribution of charged particles from a spinning spacecraft, has been built for the AMPTE and GIOTTO spacecraft. The novel features are the use of 2600 of deflection in a spherical plate electrostatic analyser to obtain energy discrimination simultaneously with dispersion in angle and the use of a microchannel plate with position-sensitive readout to obtain the angular distribution. The sensor achieves a field of view greater than 1400; a well-defined and nearly-ideal shape for the acceptance volume in velocity space and a relatively large geometric factor