An investigation of a wide angle particle analyzer for the fast measurement of plasma distribution functions

Many particle analyzer designs exist to measure plasma energy/pitch angle distributions over energy ranges of less than 1 eV to greater than 10 keV. Such devices typically employ restrictive apertures and fields to direct the particles from a "resolution window" of energy/pitch angle space onto a collector. For space plasmas, the small transmitted currents usually must be measured with the aid of particle counters, introducing a sample time which is inversely proportional to the size of this window. We propose here a device which employs no apertures or counters, but consists of an uncovered partitioned collecting surface in a varied electromagnetic environment. A procedure is developed for deconvoluting the collected partition currents to yield the plasma distribution function, although the numerical verification of this procedure may contain potential problems of ill-conditioning and requires further refinement. The device is shown to be feasible for measuring eight energy channels with a pitch angle resolution of about 10...