The CERN Antiproton Accumulator clearing system with ion current measurements as a residual neutralization diagnostic

During the first five years of operation of the Antiproton Accumulator (AA), a whole set of limiting phenomena induced by the residual neutralization by ions was observed and identified: charged dust particles causing beam blow-up, dipolar and quadrupolar coherent instabilities, and excitation of high-order, nonlinear resonances. During construction of the Antiproton Collector (ACOL), the AA was upgraded to cope with the higher antiproton flux. New clearing electrodes were added together with individual computer control of applied clearing voltage and acquisition and recording of clearing currents. A general description of the new AA ion clearing system is given together with a first account of the clearing current´s behavior. The new, computer-controlled clearing system based on specially designed electrometers capable of measuring each individual clearing current in the pA range is being commissioned