Pulse shapes from particles traversing Coulter orifice fields

Abstract

A jet 'directer' is described which permits particles to be directed along selected trajectories through a Coulter orifice. The resulting current waveshapes are seen to be characteristics of the paths taken by the particles. No evidence of the effect of the motion of charged particles on the waveshapes was detected which supports the theoretical prediction of the small magnitude of this effect. The waveshapes from known paths, when examined in the light of measured or calculated electric fields in these orifices, support a direct relationship between the resistive component of the instantaneous current amplitude and the magnitude of the local electric field at the position of the particle. In short Coulter orifices a region of uniform axial electric field is found midway between the orifice axis and the edge. Neither the axis nor the edge has regions of axial uniformity. Only spheres sized while traversing the region of uniform field will produce a true size distribution in these short orifices.