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Locking observed in XP207 for n e = 1-1.510 19 m -3

Locking observed in XP207 for n e = 1-1.510 19 m -3. 800kA 4.5kG LSN. XP-306: Parametric dependence of low-density locked-mode threshold. Extend comparison w/ theory scalings to different B T How does density threshold scale with B T and T e ?

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Locking observed in XP207 for n e = 1-1.510 19 m -3

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  1. Locking observed in XP207 for ne = 1-1.51019m-3 800kA 4.5kG LSN J. Menard - Review for XP-415, December 17, 2003

  2. XP-306: Parametric dependence of low-density locked-mode threshold • Extend comparison w/ theory scalings to different BT • How does density threshold scale with BT and Te? • Determine critical rotation frequency at low density • Use NBI pulses to increase rotation, turn off mode  change mode natural rotation and density threshold • Investigate low-density error-field amplification • Use higher-power NBI to reach hard no-wall b limit just prior to nominal mode locking time. • Then, reduce PNBI to reduce b and avoid hard collapse • Does EF amplification happen - locked mode signal return? • Measure helical structure of locked mode • If new internal RWM/EF sensors are operational, compare in-vessel signatures to ex-vessel & measure up/down asymmetry. J. Menard - Review for XP-415, December 17, 2003

  3. n=1 tearing mode Equilibrium response Mode locks Good locked mode data obtained last year Locked-mode sensors indicate some error field remains: • Mode-locking observed at lower ne, BT • Modes still lock to preferred locations • 800kA, 21019 m-3, 3.5kG • Locking measured as a function of density, toroidal field, and momentum input (beam blips). • In XP-415,want to repeat with: • New internal sensor data • Compare mode structure to that obtained with locked-mode coils • Edge Rotation Diagnostic • Supplement CHERs system • High-res CHERs rotation profiles • Only have paper copies of profiles J. Menard - Review for XP-415, December 17, 2003

  4. Locking dynamics depends strongly on density 800kA, 3.5kGauss, LSN discharges Line average density = 2.3  1019 m-3 800kA, 3.5kGauss, LSN discharges Line average density = 2.2  1019 m-3 J. Menard - Review for XP-415, December 17, 2003

  5. Locking dynamics depends on vf, b (?) • With NBI-driven rotation, tearing mode propagates in co-current direction: • Mode grows faster, locks earlier with NBI • Tearing mode naturally born propagating in counter direction: w*e or electron drift? • At low density, mode eventually locks bN= 0.7 No NBI bN= 2 1.5MW NBI heating (t=140-240ms) J. Menard - Review for XP-415, December 17, 2003

  6. New internal sensors will be ready for run:Each primary plate will measure B and BP • Full toroidal coverage • 24 B and 24 BP • Each 12 above, 12 below • B measured by single turn loop • Embedded in tiles • Centered in plate • BP measured at ends of primary plates • Glass insulated Cu wire wound on macor forms • SS304 shields Thermocouple connectors allow easy installation and upgrade potential (PnP) J. Menard - Review for XP-415, December 17, 2003

  7. Goal of XP-415 • Primary objective is to repeat threshold scans with additional/improved diagnostics to improve physics understanding. • Locked modes easy targets for comparing internal sensor to LM sensor response • Do sensors show expected helical structure? • Supplement CHERs profiles with ERD to better understand rotation profile dynamics before and during mode locking. • Asking for ½ day (but, more is always better). • Would really like beams – not abs. necessary J. Menard - Review for XP-415, December 17, 2003

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