Experimental Plan for the New Wall-Actuated Scanning Probe (WASP) Noah Smick, Brian Labombard C-Mod Ideas Forum, December 2006 Wall-Actuated Scanning Probe (New for ’07) (To Be Replaced with a second WASP) New Capabilities: Measurements up to and beyond LCFS Multi-Electrode Capabilities (e. g. fluctuation induced fluxes) Cross-field flow information Well-controlled plunge dynamics Diagnostic Arrangement

Experimental Plan for the New Wall-Actuated Scanning Probe (WASP) Noah Smick, Brian Labombard C-Mod Ideas Forum, December 2006 Planned Experiments: New diagnostic “shake down” run day during start-up to exercise probes, optimize scan motion. There are several issues to address here: Verify Mechanical functionality of the probe Explore our ability to control probe plunge dynamics by adjusting driving waveforms Explore the probe physics associated with the new Gundestrup-like probe tip geometry vs. old probe tips. Are the small systematic differences in parallel flow velocity with new tip geometry on 6/13/06 real? Which is correct? Do we trust the ability of these probes to measure cross-field flow? Are the general flow trends previously measured reproduced? 1 startup run day: ohmic 5.4T 800kA with density scan, USN LSN DN, to touch with previously measured flow data. All three scanning probes and divertor probes to be operated. L-Mode Experiments: Get inner wall flow data during SSEP scan to inform SOL flow modeling (UEDGE, per request by A. Pigarov, UCSD). Data at left shows SSEP scan with density measurements [1]. What do the flows do across the region of steep density gradient? 1 run day 5.4T 800kA with Density, SSEP scan including USN, LSN and near-balanced DN’s. 1st Gundestrup-like probe Current Gundestrup-like probe tip, to be installed on all C-Mod scanning probes for ‘07 [1] Boswell, et al., Plasma Phys. Control. Fusion 46 (2004) 1247.

Experimental Plan for the New Wall-Actuated Scanning Probe (WASP) Noah Smick, Brian Labombard C-Mod Ideas Forum, December 2006 Planned Experiments: L-Mode Experiments: Revisit , mhd SOL phase space. This is an open mini-proposal (#409) that can benefit from the enhanced flow-measurement capabilities of the new probes. 1 run day to revisit standard discharges and continue to explore phase space, including new HFS and cross-field flow data Some models predict flow reversal in the HFS near-SOL. Increased operational depth of WASP will allow us to investigate this. Could the flow loop be closed by an inward pinch on the HFS? The multi-electrode WASP can address this by measuring fluctuation induced fluxes. H-Mode Experiments Probe Ohmic H-Mode transitions (See Labombard, “Ohmic L-H Threshold Experiments”, this forum.) Potential for Operation in RF Heated H-Modes without rectification-corrupted Te measurements (based on single-pass absorption of RF waves)  pedestal physics, QC mode investigations. Parallel Flow Reversal on HFS WASP Probe A. Pigarov, “Asymetries in Unbalanced Double-Null Divertor Configurations”, Oral presentation, 48th Annual Meeting of the Division of Plasma Physics, Philadelphia, PN, 31 Oct. 2006