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Events on Monday, December 7th, 2020

Academic Calendar
All classes move to virtual format for the remainder of the semester
Abstract: *Note: actual end time may vary.*
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Plasma Physics (Physics/ECE/NE 922) Seminar
Demonstration of helium exhaust enhancement during resonant magnetic perturbation (RMP) field application at DIII-D
Time: 12:00 pm
Place: Zoom Meeting
Speaker: Edward Hinson, UW Engineering Physics department
Abstract: It is shown for the first time in a diverted tokamak that
key metrics for continuous fusion, effective helium particle
confinement time, 𝛕_p*He, and its ratio with energy confinement,
𝛕_p*He/𝛕_E, were reduced by a factor of 2-3 during suppression of
edge localized modes (ELMs) by resonant magnetic field perturbations
(RMPs) over the unperturbed ELMy case. Reduced 𝛕_p*He during RMP was
observed in the core, edge, and pump plenum, where higher helium
pressure and concentration were also found. Elevated ionized helium
line emission during ELM suppression, with a decay time matching
𝛕_p*He, was measured at the inner strike point, suggesting more
helium in the unconfined region. These observations suggest that
processes during application of RMPs better retain helium at the edge,
in excess of that expected from deuterium ‘pumpout,’ where it is
pumped more quickly. A multi-reservoir model, derived from a finite
volume approximation of the continuity equation with diffusive and
convective transport, fits the helium time evolution at each of the
above-mentioned measurements well. Transport parameters obtained from
these fits indicate the data are consistent with strongly increased
transport of helium in the separatrix region during RMP application,
although higher core transport is also found. These findings, which
were obtained in ITER-shaped plasmas, provide evidence that
application of RMP ELM suppression in future devices such as ITER may
be capable of matching or exceeding the helium impurity exhaust
produced by the ELM events themselves, thereby helping to avoid helium
ash buildup in a burning regime, and maintain high fusion gain.

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Meeting ID: 991 5610 7574
Passcode: 883688
Host: Paul Terry
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