Alcator C-Mod Weekly Highlights March 29, 2004 Research operations continued at Alcator C-Mod last week. Four run days were scheduled and completed. This brings the total research runtime in FY04 to 53.5 days (13.4 weeks); the operations target called for in JOULE Milestone SC7-6a is 18 weeks. Three experiments were concentrated on internal transport barrier physics and applications to advanced scenarios. One experiment was devoted to the relationship between edge plasma flows, magnetic topology and the L-H transition. Plasma operations are scheduled to continue this week. Operations ---------- A fresh boronization was carried out on Monday evening. Plasma runs were carried out Tuesday through Friday, with a total of 116 plasma discharges produced; startup reliability was 95%. Tuesday's run continued work on MP#341, concerning heating inside ITB's formed with off-axis ICRF. Up to 2MW of on-axis power was coupled to an ITB, but a H-L back transition ensued shortly thereafter. Radiated power was found to be more prevalent in these discharges than during the run on March 9, despite the recent boronization. On-axis heating at 1.4-1.5 MW was successful in clamping the density rise and increasing peak temperatures. These experiments indicate that we have not yet found a limit on additional central power in established ITB's under optimal conditions; previous limitations are probably related to the level of core radiated power. Wednesday's run of MP#305, on hysteresis in the on- and off-axis power for establishment and sustainment of ITB's, also suffered from back transitions associated with core radiation. ITB's were obtained with both high- and low-field side resonances, with the high-field side cases being more reliably produced. As found during Monday's run, off-axis power over 2MW seemed to be preferred for robust ITB formation, limiting the parameter range over which these experiments could be carried out. Thursday's run was scheduled for MP#307, "High bootstrap fraction regimes". The point of this experiment was to exploit the strong gradients in pressure and especially density obtained in two-frequency ITB plasmas to access high bootstrap fraction. The experimental plan called for decreasing the plasma current in established ITB discharges sustained by central ICRF heating. This plan required long-duration internal barriers, which were found not to be accessible under the present machine conditions. After considerable exploration of parameter space, it was decided to turn the remainder of the run over to the experiment scheduled for Friday, MP#384. The experiments on MP#384 were aimed at exploring the effect of recycling at the inner divertor nose on SOL/core momentum coupling and the (perhaps related) issue of L-H power thresholds in discharges which limit on the divertor nose compared to standard lower single null equilibria. An additional goal of these experiments was to map the effect of the inner gap on the threshold power and on the edge flows. These experiments were successful, completing the MiniProposal. For three equilibria, normal lower null, a lower null with the separatrix grazing the inner nose, and discharges strongly limited on the nose, the threshold power was found to be essentially independent of topology at low density (nebar~1.1e20/m^3) and at most weakly dependent (20% higher threshold for limited case) at 1.6e20. Good flow data were recorded by probes (SOL), Chromex (near separatrix), and HIREX (core). For lower null configurations (clear of the nose), a scan of the gap to the inner midplane over the range 0