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Recent Results from the STOR-M Tokamak. A .Hirose, M. Dreval, S. Elgriw, O. Mitarai(1), A. Pant, M. Peng(2), D. Rohraff, A.K. Singh(3), D. Trembach, C. Xiao Plasma Physics Laboratory University of Saskatchewan, Canada - PowerPoint PPT Presentation
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Recent Results from the
STOR-M TokamakA .Hirose, M. Dreval, S. Elgriw,
O. Mitarai(1), A. Pant, M. Peng(2), D. Rohraff, A.K. Singh(3), D. Trembach,
C. XiaoPlasma Physics Laboratory
University of Saskatchewan, Canada(1) Institute of Industrial Science and Technical Research, Kyushu
Tokai University, Kumamoto, Japan(2) Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA(3) Present address: Dept. of Physics, Utah State Univ., Logan, Utah,
USA
IAEA TM RUSFD, October 22-24, 2007, Lisbon, Portugal
STOR-M tokamak (• H-mode studies (biasing, TH, CT), turbulence/fluctuations• AC operation• Compact torus injection
/ 46 /12 cm, 1 T, 40 kA)t pR a B I
OutlineOutline
Part I Effects of Compact Torus (CT) Injection on
the MHD Fluctuations in STOR-M Discharges
Motivations Experimental Setup Singular Value Decomposition (SVD)
Algorithm Experimental Results Future Work Summary I
Outline (cont.)Outline (cont.)Part II
Simulation of Spherical Tokamak Current Start-up by Outer Vertical Field Coils in
STOR-M Motivations STOR-ST configurations Numerical simulation of the plasma current
start-up in STOR-M ST simulation start-up experiments in STOR-M Proposed experiment of saturable iron core
operations in STOR-M Summary II
Motivations (CT/MHD)Motivations (CT/MHD)
Compact Torus (CT) injection is a promising technique to fuel large tokamak fusion reactors
Magnetic interactions between CT and tokamak plasma are important parts for ◦ CT penetration into tokamak◦ Fuel deposition
Localized fuelling may alter pressure profile
Does CT injection excite MHD instabilities?
CT toroidal field/current
Motivations (CT/MHD)Motivations (CT/MHD)
Tangential CT injection induced H-mode like phase
M=2 mode suppressed
M=2 mode reappearBefore H-L transition
M=3 mode intact(not shown here)
Experimental Setup:Experimental Setup:
12 discrete Mirnov coils evenly distributed in the poloidal direction.
Measures /dB dt
Singular Value Decomposition Singular Value Decomposition Algorithm:Algorithm:
SVD algorithm decomposes matrix
A=USVT
t
i Principal Axis
SJJ: mode energy
US
t
modes
Principal component
Experimental ResultsExperimental Results
CT is injected at t=15.25 msec MHD activities are is suppressed after CT injection MHD activities return to higher level at t=16.35
Features during the MHD reemergence phase◦ Starts with non-propagating strong signals near the
inner board◦ Followed by a propagating (rotating) m=2 mode
A dominant Principal Axis pair (PA1, PA2) an m=2 structure (Sine and Cosine parts)
Corresponding Principal components oscillating at 30 kHz seen by a fixed Mirnov coil when the m=2 mode rotates at 15 cycles/msec
The third dominant mode m=1 spatial structure Short-lived burst non-propagating the gong
mode The gong mode appears to be the precursor
triggering the MHD activities and H-L back transition
Direct spatial FFT based on 12 Mirnov raw signal evolution of the m=1 and m=2 components
The gong mode burst occurs well before the development of m=2 mode
What triggers the gong mode? Sawtooth crash in the core region near q=1 surface
excites the gong mode.
Does gong mode travel in toroidal direction? Is this also true in STOR-M? Does CT injection cause sawtooth crash as the
pressure build up?
Future Work:Future Work:
Install another poloidal array offset from the first by 180° in toroidal direction
Future Work (cont.):Future Work (cont.):
Develop Soft X-ray (SXR) pin-hole cameras to investigate◦ Relation between Core and edge MHD oscillation◦ Relation between sawtooth crash and gong mode
Summary I:Summary I:
CT injection suppressed MHD during the induced H-mode like phase.
Reemergence of the MHD may have terminated H-mode phase.
The return of the relatively large propagating m=2 MHD oscillations is led by a non-propagating, gong mode like m=1 burst.
Further investigation is necessary to better understand the effects of CT injection on MHD activities in tokamak plasma.
Part IIPart II
Simulation of Spherical Tokamak Current Start-up by Outer Vertical Field Coils in
STOR-M
Motivations (ST Current Start-Motivations (ST Current Start-up)up)
Small aspect ratio spherical tokamaks (STs) have limited space for central solenoid (CS) for current ramp-up
Current start-up without CS is necessary for Component Test Facility, CTF, (R=1.2 m, a=0.8 m, A=1.5, Bt=2.5 T, Ip=16 MA, k=3.2, Pf=300 MW)
Small iron core for the current start-up was proposed by Nishio for Vector
STOR-M Configurations
STOR-ST Configurations (cont.)
Numerical simulation of the
plasma current start-up in STOR-M magnetic field
induced by the current through various poloidal field coils
imaging field due to iron core is included
Numerical simulation results
Experimental results
Proposed experiment of saturable iron core operations in STOR-MSTOR-ST current terminates at ~22 msec
The iron core became nearly saturated air core transformer
Third bank will be used to sustain the current
Proposed experiment of saturable iron core operations in STOR-M
Summary IIIron core ST current start-up using
vertical field windings has been successfully simulated using STOR-M
Experimental results agree well with numerical calculations
Experiments for saturable iron core current start-up and maintenance have been proposed
Thank you!