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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-3775
DTSTART:20151012T170000Z
DTEND:20151012T180000Z
DTSTAMP:20260419T110403Z
LAST-MODIFIED:20150930T161313Z
LOCATION:2241 Physics Bldg 
SUMMARY:H-mode and ELM Studies at Near-Unity Aspect Ratio\, Plasma Phy
 sics (Physics/ECE/NE 922) Seminar\, Kathreen Thome\, Engineering Physi
 cs
DESCRIPTION:The H-mode confinement regime is achieved at near-unity as
 pect ratio (A < 1.2) in the Pegasus Toroidal Experiment via high-field
 -side fueling and low edge recycling. Ohmic H-mode is attained in both
  limited and diverted magnetic topologies. This regime is characterize
 d by: reduced Dα emissions\; increased core rotation\; increased cent
 ral heating\; formation of edge current and pressure pedestals\; and i
 mproved energy confinement. The H-mode power threshold\, PLH\, behaves
  quite differently at low-A when compared with high-A operations. PLH/
 PLH_ITPA08 increases sharply as A is lowered and no difference in PLH 
 for limited and diverted plasmas is observed at  A ~ 1.2. No minimum i
 n PLH with density is observed. Some of these results are consistent w
 ith the FM3 model for the L-H transition [1]. Two classes of ELMs have
  been observed. Small\, Type III-like ELMs are present at low input po
 wer and have n ≤ 4. At POH >> PLH\, they transition to large\, Type-
 I-like ELMs with intermediate 5 < n < 15. The Type III ELM magnetic st
 ructures behave opposite to that observed in high-A plasmas\, with n m
 uch higher\, presumably due to the naturally higher J/B peeling mode d
 rive at low-A. Long-sought measurements of the Jedge(R\,t) pedestal co
 llapse during an ELM event show a complex\, multimodal pedestal collap
 se and the subsequent ejection of a current-carrying filament.
URL:https://www.physics.wisc.edu/events/?id=3775
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