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PRODID:UW-Madison-Physics-Events
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SEQUENCE:1
UID:UW-Physics-Event-8243
DTSTART:20230417T170000Z
DTEND:20230417T230000Z
DTSTAMP:20260414T071359Z
LAST-MODIFIED:20230403T204719Z
LOCATION:2241 Chamberlin Hall
SUMMARY:Schnack Memorial Seminar: Simulating Transient Excitation of N
 eoclassical Tearing Modes\, Plasma Physics (Physics/ECE/NE 922) Semina
 r\, Eric Howell\, Tech-X Corporation
DESCRIPTION:Disruption avoidance and mitigation strategies are needed 
 for ITER and future fusion pilot plants. Neoclassical tearing modes (N
 TMs) are a leading physics cause of disruptions in present-day experim
 ents\, and predictive NTM models are vital for the success of burning 
 plasma tokamaks. NTM growth is driven by a helical bootstrap current d
 eformation that results from pressure flattening across an island. NTM
 s are metastable states that require a seed island to grow. The seed i
 slands are generated by ELMs\, sawteeth\, and other transients. Nonlin
 ear simulations study the transient excitation of NTMs.  Simulations u
 se reconstructions of DIII-D ITER baseline scenario discharges. The do
 minant neoclassical effects\, including the bootstrap current drive\, 
 are modeled using heuristic fluid closures for neoclassical stresses. 
 Magnetic perturbations are transiently applied to excite a growing NTM
 . These perturbations act as surrogates for ELMs. A Goldilocks effect 
 is observed with regard to the applied perturbation amplitude. If the 
 amplitude is too small\, no NTMs grow. If the amplitude is too large\,
  a 2/1 NTM grows robustly immediately following the pulse. If the ampl
 itude is just right\, then the 2/1 NTM grows in two phases: an initial
  slowly growing phase followed by a fast robustly growing phase. An en
 ergy transfer analysis shows that the early slow growth phase is parti
 ally driven by nonlinear interactions with higher-n core modes. The la
 ter robust growth phase is described by the modified Rutherford equati
 on. <br>
\n<br>
\nThe work is funded by the US Department of Energy
URL:https://www.physics.wisc.edu/events/?id=8243
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