DESIGN STUDIES FOR AN ADVANCED ECR ION-SOURCE

Magnet design codes, plasma dispersion solvers, and particle-in-cell ( PIC) simulation codes have been used to arrive at the first step in th e design of an advanced ion source based on electron cyclotron resonan ce (ECR) technology. The advanced concept design uses a minimum-B magn etic mirror geometry which consists of a multicusp magnetic field to a ssist in confining the plasma radially, a flat central field for tunin g to the ECR resonant condition, and specially tailored mirror fields in the end zones to confine the plasma in the axial direction. The mag netic field is designed to achieve an axially symmetric plasma ''volum e'' with constant mod-B, which extends over the length of the central field region. This design, which strongly contrasts with ''surface'' E CR zones characteristic of conventional ECR ion sources, results in dr amatic increases in the absorption of rf power, thereby increasing the electron temperature and ''hot'' electron population within the ioniz ation volume of the source. The creation of a volume rather than a sur face ECR zone is, therefore, commensurate with the generation of highe r beam intensities, higher charge states, and a higher degree of ioniz ation. A summary of the results of these studies is presented in this report.