Measurement of the fluctuations and LANL LLNL Lodestar ELMs using - - PowerPoint PPT Presentation

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Measurement of the fluctuations and LANL LLNL Lodestar ELMs using - - PowerPoint PPT Presentation

Aug 14, 2022 29 likes •341 views

Supported by Columbia U Comp-X General Atomics INEL Johns Hopkins U Measurement of the fluctuations and LANL LLNL Lodestar ELMs using fast camera in NSTX MIT Nova Photonics NYU ORNL PPPL PSI SNL UC Davis UC Irvine UCLA Nobuhiro

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Supported by

Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics NYU ORNL PPPL PSI SNL UC Davis UC Irvine UCLA UCSD U Maryland U New Mexico U Rochester U Washington U Wisconsin Culham Sci Ctr Hiroshima U HIST Kyushu Tokai U Niigata U Tsukuba U U Tokyo JAERI Ioffe Inst TRINITI KBSI KAIST ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching U Quebec

Measurement of the fluctuations and ELMs using fast camera in NSTX

Nobuhiro Nishino 1), L.Roquemore2), T.Biewer2), S.J.Zweben2), R.Maqueda3), R.Maingi4), C.Bush4), and NSTX team

1) Hiroshima University 2) PPPL 3) Nova Photonics 4) ORNL

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Introduction

  • Fast camera measurement

– Divertor camera using midplane port (STW2002) – Divertor tangential camera (STW2004)

  • A proposal under US-Japan collaborative activity since 1998

– Center stack camera (STW2004) – GPI with side view (STW2002-)

  • Results and discussion

– Fluctuations and ELMs – Trial to categorize fluctuations and ELMs?

  • Conclusion
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3 Fast camera with midplane (2002) Fast camera with divertor tangential view (2004) Fast camera with center stack and midplane view(2004)

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Field of view of the divertor fast camera (2004)

  • Approximate camera

field of view (yellow box, but left side is limited by passive plate)

Nishino (U. Hiroshima), Roquemore, Maingi (ORNL)

Divertor gap Center stack

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Categories of fluctuations and ELMs

  • Structure difference (Effect on the confinement?)

– Filament – Wave pattern near the inner separatrix – L-H transition near the inner separatrix – L-H transition near the outer separatrix

  • Effect on the energy confinement

– Giant ELM (TYPE I) – Medium/Intermediate ELM (TYPE I and TYPE II?/III) – Small ELM (TYPE II?/III) – Small ELM (do not lead to a severe loss of stored energy)

  • Labeled TYPE V (authorized?)

– Inner region ELM in DN configuration

  • Labeled TYPE VI (private)
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Filament with tangential view

  • 0.30-0.34sec

center

There are many filaments in outer region.

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Wave pattern (finger) near the inner separatrix and small ELMs

  • 0.47-0.484sec

center

Filament fingers from inner region can be seen.

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L-H transition near the inner separatrix

  • 0.22-0.239sec

center

Fluctuations are suppressed during L-H transition.

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L-H transition near the outer separatrix

  • Some spatial structure is

seen in H-mode

center

  • 0.21-0.22sec
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GPI Diagnostic setup in NSTX

  • Use re-entrant port and linear gas manifold.
  • Use He, D2, or Ar puffs.
  • Use beam-splitter and PMTs (100 kHz bandwidth) for discrete fast chords.

Gas manifold Side-viewing re- entrant window Local magnetic field

GPI view

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Gas puff from linear manifold viewed across torus

NSTX

Shot 108975

0.9 MA - 0.35 T HeI filter (587.6 nm) 74 µs exposure Photron Fastcam-Ultima SE

Manifold

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0.0E+00 1.0E+04 2.0E+04 3.0E+04 4.0E+04 5.0E+04 6.0E+04 7.0E+04 8.0E+04 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 0.35 0.36 0.37 time (sec) intensity

HeI intensity in GPI experiment

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L & H-mode in GPI experiment (STW2002)

  • View image of L and H-modes during He gas puff by mid plane port
  • There are many filaments in L-mode, and a few filament in H-mode.
  • No new structure has found in L and H-modes.

H-mode L-mode

40500fps with He I filter (587.6nm) #108979

Many filaments are seen Filaments are seen sometimes

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L-H transition near the outer separatrix

  • What is the key to understand

H-mode?

  • Need complete H-mode theory
  • 0.21-0.22sec
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Fluctuations

  • Wave pattern (finger) observed frequently in the inner region
  • Many filaments in L-mode
  • Less filament in H-mode, but not zero
  • Some spatial structure is found in H-mode, and this structure

and filament can exist together

  • What is the filaments?

– Possibly High density region from GPI

  • What is the key of H-mode physics?

– Filament is not the key!?

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Giant ELM or TYPE I

  • Many filaments are seen outer region
  • f separatrix.
  • It looks like inner region fluctuation is

independent of filaments

0.23-0.26sec

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Giant ELM

  • 0.53-0.55sec
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Typical waveforms of Medium ELM

  • ELM with precursor (left) and without precursor (right)
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Medium ELM (TYPE III with 2kHz MHD precursor)

  • 0.364-0.381sec

center

Precursor with MHD odd-n signals

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TYPE III with precursor?

  • 0.297-0.31sec

center

Week precursor with MHD odd-n signals

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TYPE III without precursor ?

  • 0.525-0.537sec

center

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TYPE V and Giant ELM

  • H-mode structure and

filament can exist together

0.34-0.383sec

center

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0.0E+00 1.0E+05 2.0E+05 3.0E+05 4.0E+05 5.0E+05 6.0E+05 7.0E+05 2.5E-01 3.0E-01 3.5E-01 4.0E-01 4.5E-01 5.0E-01

TYPE V with midplane view (STW2002)

TYPE V ELMs occur periodically. But 1-2kHz movement can be seen using FFT <=> TYPE III precursor

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Auto-correlation function of each pixels (STW2002)

  • 2D auto-correlation function plotted

shown by arrows.

Original image

Auto-correlation function Power spectrum

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  • Continued. during small ELMs

(STW2002) – 4-8

4 5 6

1-2kHz peak spectra along the helical line are founded (not shown in figure)

7 8

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Origin of small ELM (TYPE V)

  • 0.329-0.358sec

center

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ELMs in the inner region in DN plasma

  • It moves along the field line.

– Its speed can be deduced by camera data & Mirnov.

  • Field of view

– Center 40500FPS

  • 64x64 pixels

– Background 4500FPS

  • 256x256 pixels

– (these shots are different.)

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Inner region ELMs in DND configuration

  • Inner region

ELMs bounced near the center stack

  • Only DND

configuration

  • What is the

physics?

– MHD or E- Static

  • Locations of

two X-points?

Center stack gas puff

center

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TYPE of ELMs in NSTX

  • TYPE I

(ideal ballooning mode)

  • TYPE II?

(access to second stability)

  • TYPE III

(resistive ballooning mode)

  • TYPE V

(New, Physics?)

– Outer region in LN configuration (almost)

  • TYPE VI？ （Newer, Physics?)

– Inner region in DN configuration (always)

  • An attempt has been made to categorize the types of ELMs more
  • precisely. Although useful, the definitions are somewhat imprecise.

(from “Tokamaks” by J.Wesson)

  • Too many data are to be analyzed, and the analysis will continue.
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Conclusion

  • The fact is that

– Many ELMs and fluctuations are observed in NSTX. – In particular, new ELMs (labeled TYPE V and TYPE VI) are found very recently.

  • But (to me)

– the physics for new ELMs are needed. – Also, a filament model and the complete H-mode theory are necessary.

  • Measurement system

– Fast divertor camera is very useful for measurement of fluctuations and ELMs. – Additional information

  • Two fast cameras will be provided with NSTX to measure the inner region

plasma and the divertor plasma simultaneously next year.