and nonlinear coupling O Sauter Ecole Polytechnique Fédérale de Lausanne EPFL Swiss Plasma Center SPC Lausanne Switzerland httpinfoscienceepflchrecord212765 Outline Several ID: 232122
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Slide1
Multiple NTM modes in experiment and nonlinear coupling
O. SauterEcole Polytechnique Fédérale de Lausanne (EPFL)Swiss Plasma Center (SPC)Lausanne, Switzerlandhttp://infoscience.epfl.ch/record/212765Slide2
Outline
Several cases, mainly taken from published dataCoupling (locked frequencies
)
can
have
little
effects
or
stabilizating
effects
No «
dramatic
»
effects
observed
so
far…Slide3
«Standard» case when
increasing powerR. Buttery, Nucl. Fus. 43 (2003) 69, JETIncreasing power4/3 appearsThen 3/2Finally 2/1, which locks «whole» plasma(E. Lazzaro, PoP 9 (2002) 3907)Slide4
«Standard» case when
increasing powerDIII-D/JET similaritiesAt 2/1 onset, little change of 3/2, which continues.T. Hender et al, IAEA 2002, JET
While
2/1 locks, 3/2
can
lock to 2/1
with
little
effectsSlide5
Large trigger can
yield several modesR. Buttery, IAEA 2004, JET3 modes triggered together2/1 leads the lockingTermination seems similar to when only 2/1 mode presentSlide6
TCVSlide7
Non-harmonic
couplingD. Raju, PPCF 45 (2003) 369Slide8
4/3 effect on 3/2 mode
D. Raju, PPCF 45 (2003) 369Slide9
4/3 effect
on 3/2 mode=> constant D’coupling<0O. Sauter, PPCF 44 (2002) 19992 consecutive ST crashestrigger and stabilize 4/33/2 evolution consistentwith a constant negativeD’ in modif. Ruth eq.
JETSlide10
3/2 preemption
may also help for 2/1 preemptionD. Kim, PhD thesis No 6539, EPFL, 20152/1 mode avoided with 3/2 preemption: preliminary resultsMay indicate coupling, marginal conditions, q profile changes: to checkDifficult to trigger 2/1 without first a 3/2 mode…
TCVSlide11
Changing q profile does
play a roleE. Lazzaro, Nucl. Fusion 55 (2015) 093031D. Kim, PhD thesis No 6539, EPFL, 2015Same power ramp but different co/cnt components of beamsOnset at different power levels3/2 mode contribution
before
2/1
onset
is
different
as
well
TCVSlide12
Some conclusions
Multiple modes can co-exist without coupling (most cases)Usually the mode with larger r(q=m/n) dominatesMode can couple: best analysis is bi-coherenceNeed to check exact frequency couplingNeed to check effective effects on island widths(t) (nonlinear/frequency
coupling
does
not
necessarily
mean
«
strong
»
coupling
)
Word of caution: 2/1 modes tend to
kill
rotation over whole plasma thus all modes "will" «lock» during the process
Role if any of 3/2 preemption on 2/1 avoidance may provide more insight