1. 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

2. 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.

3. 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