Kinetic Alfvén waves driven by rotating magnetic islands K. L. Wong, K. Tritz, D. R. Smith, Y. Ren, E. Mazzucato, R. Bell, S. Kaye, K. C. Lee NSTX Physics Meeting LSB318, PPPL Feb 1, 2010 NSTX NSTX Supported by College W&M Colorado Sch Mines Columbia U CompX General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Washington U Wisconsin Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec
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Kinetic Alfvén waves driven by rotating magnetic islands K. L. Wong, K. Tritz, D. R. Smith, Y. Ren, E. Mazzucato, R. Bell, S. Kaye, K. C. Lee NSTX Physics.
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Kinetic Alfvén waves driven by rotating magnetic islands
NSTXNSTX Meeting name – abbreviated presentation title (last name) Month day, 20**
KAW quasi-modes excitated by rotating magnetic islands- this mechanism should be more efficient than 3 wave coupling
• Perturbed B of pure m/n=2/1 island near q=2 surface:
b(,,) = b()exp[i( - 2)]
• Include other toroidal harmonics: b(,,) =n bn(,) exp(in)
• Neoclassical tearing mode propagates in the plasma along the direction
with freq. ’f i where f < 1
• The q=2 surface rotates with angular freq in the laboratory frame,
and the 2/1 mode freq. is: ’+k.V= ’+kV+kV =
because i<<at low mode numbers, and V<<V .
• bn(,) has freq n in the laboratory frame.
• The induced Erf =Vxbn , i.e., the rotating island acts like an RF antenna driven at
various harmonic freq n and KAWs at these frequencies are excited.
• Island location: R~122-137 cm, scattering volume at R~123 cm (at island edge)13
NSTXNSTX Meeting name – abbreviated presentation title (last name) Month day, 20**
KAW not new - was observed in TFTR 15 years ago, - the excitation mechanism is new & common in tokamaks
• Ref: Wong et al., Phys. Lett. A. 244, 99 (1996) – mode conversion from TAEs- fast ions from ICRF; scattering from 5 Watt 60GHz (5mm) probing beam, no beam dump.
“ghost feature” near f~0
• NSTX data is interesting because of their association with locked mode• Many KAWs appear in plasmas with violent MHD activities shortly
before locking• Can we use this as a locked mode / disruption precursor ?
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NSTXNSTX Meeting name – abbreviated presentation title (last name) Month day, 20**
Conclusion: Spectrum with 40 peaks is scattering from KAWs driven by rotating 2/1 islands
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Generalized Interferometry effect : n More peaks , but . . . . .
Transition from n=2 to n=1 at 0.48s: flat to peaked ne(r),f(r)