INWARD ELECTROSTATIC PRECIPITATION OF INTERPLANETARY PARTICLES

An inward precipitator collects particles initially dispersed in a gas throughout either a cylindrical or spherical chamber onto a small cen tral planchet. The instrument is effective for particle diameters grea ter than about 1 mum. One use is the collection of interplanetary dust particles which are stopped in a noble gas (xenon) by drag and ablati on after perforating the wall of a thin-walled spacecraft-mounted cham ber. First, the particles are positively charged for several seconds b y the corona production of positive xenon ions from inward facing need les placed on the chamber wall. Then an electric field causes the part icles to migrate toward the center of the instrument and onto the plan chet. The collection time (of the order of hours for a 1 m radius sphe rical chamber) is greatly reduced by the use of optimally located scre ens which reapportion the electric field. Some of the electric field l ines terminate on the wires of the screens so a fraction of the total number of particles in the chamber is lost. The operation of the instr ument is demonstrated by experiments which show the migration of carbo n soot particles with radius of approximately 1 mum in a 5-cm-diam cyl indrical chamber with a single field enhancing screen toward a 3.2 mm central collection rod.