ICRF Experiments in Alcator C-Mod

One challenge to ion cyclotron range of frequency (ICRF) utilization is its interaction with the edge plasma. With a field aligned antenna, the impurity sources at the antenna are dramatically reduced, but the enhanced plasma potentials are yet present. An emerging explanations is that the ICRF convective cell creates a local source at the RF antenna and modifies the impurity transport/source away from the antenna. To test the importance of ICRF convective cell, the impurity source at the antenna is compared from 2-8 T. Furthermore, experiments have performed to investigate changes in impurity penetration/source by puffing known amounts of N impurity from four locations that have different mappings to an ICRF antenna energized as a function of RF power. In C-Mod, overall plasma performance has been observed to be dependent on RF absorption efficiency and a new three-ion ICRF scenario has been identified that has efficient RF power absorption. Initial experiments will investigate the heating and RF flow drive effectiveness. Latest results and analysis will be presented.