Neutralization of positive particle beams by electron trapping

Initial results are presented of a planned series of experimental tests of positive ion beam neutralization, involving transverse space charge studies of a 720 keV 60mA H+ beam in a drift region of 4.6 meters. Two conclusions drawn from the data are: (1) the change in transmission observed is consistent with complete neutralization in the drift pipe for grounded or negative electrodes, and with complete de-neutralization in the case of greater than +240 V electrodes; and (2) background gas ionization cannot be the main source of electrons