SPECS, a Versatile Space-Qualified Detector of Charged Particles

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Abstract
A versatile instrument code named SPECS (for Switched Proton Electron Channeltron Spectrometer) has been developed for measurement of charged particles in space. Particles entering the device pass between a pair of deflection plates across which is established a voltage Vi. Particles of a given charge and different energies are then deflected into a set of five channeltron devices located on one side of the deflection plates, while particles of the opposite polarity but comparable energies are deflected into a funneltron located on the opposite side of the plates. Thus, electrons and protons are detected simultaneously in a total of six differential energy intervals. The voltage Vi is then changed over six steps: ±35 V, ±350 V, and ±3500 V. In this way electrons are measured over an energy range of about 50 electron volts (eV) to about 100 000 eV. Protons are measured over the same energy range, with the lowest detectable energy set by the intrinsic channeltron efficiency of detection of positive ions at some hundreds of electronvolts. The thirty‐six energy channels can be measured in an adjustable cycle time as short as 1 sec. Stepping can be internally or externally synchronized. Different versions of the device have been built for numerous rocket and satellite applications, with weight between 900 and 1600 g, and power less than 1.5 W. Five small units have been flown to date on Javelin rockets, and the larger will be put into orbit in the satellites code‐named Owls 1 and 2 and Aurora 1, while another set will be deployed by the astronauts on the lunar surface. The scientific advantages and flexibility of the units are described.