electrons within the MST1 TCV15-1.3.5 project J. Decker, G. Papp, - - PowerPoint PPT Presentation

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electrons within the MST1 TCV15-1.3.5 project J. Decker, G. Papp, - - PowerPoint PPT Presentation

Aug 01, 2023 381 likes •588 views

2016 TCV experiments on runaway electrons within the MST1 TCV15-1.3.5 project J. Decker, G. Papp, S. Coda, B. Duval, P. Blanchard, D. Choi, C. Galperti, B. Labit, P. Marmillod, O. Sauter, U. Sheikh, D. Testa, D. Carnevale, B. Esposito, O.

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SLIDE 1

2016 TCV experiments on runaway electrons

within the MST1 TCV15-1.3.5 project

  • J. Decker, G. Papp, S. Coda, B. Duval, P. Blanchard, D. Choi,
  • C. Galperti, B. Labit, P. Marmillod, O. Sauter, U. Sheikh, D. Testa,
  • D. Carnevale, B. Esposito, O. Ficker, M. Gobbin, P. Martin,
  • R. Paprok, Y. Peysson, V. Plyusnin, C. Reux, F. Saint-Laurent
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SLIDE 2

Objectives of TCV15-1.3.5

  • Establish reliable scenario for runaway electron plateau formation
  • Characterize RE generation and mitigation
  • Determination of the critical field
  • Effect of plasma shaping on RE generation and mitigation
  • Effect of MHD instabilities on RE confinement
  • Control of RE beam position

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 3

Systems and Diagnostics

  • TCV : B = 1.45 T, R = 89 cm, a = 25 cm, κ < 2.8, |δ| < 1.0
  • MGI via DMV (Ar, Ne, …)
  • HXRS : HXR tomographic spectrometer
  • CdTe detectors, 2 cameras (1 vertical and 1 horizontal)
  • PMTX : photomultiplier outside the vessel
  • Usual tokamak diagnostics (magnetics, FIR, TS, SXR, …)

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 4

52716 : full OH->RE conversion

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 5

52717: RE beam «natural» decay

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 6

Effect of pre-MGI density

  • 52717 : ne = 1.5x1018 m-2
  • 52743 : ne = 2.0x1018 m-2
  • 52742 : ne = 2.5x1018 m-2
  • Importance of pre-MGI

RE fraction?

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 7

tMGI vs pre-MGI RE density

neFIR = 0.25 f.

  • 53326 : tMGI = 0.32s
  • 52742: tMGI = 0.47s
  • 53328: tMGI = 0.72s
  • RE beam generation if pre-

MGI RE density is sufficient

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 8

IOH control

  • 52717 : dIOH/dt = 0
  • 52724 : dIOH/dt < 0
  • 52725 : dIOH/dt > 0
  • Reliable RE beam scenario
  • RE plateau current control

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 9

Second MGI – Ne injection

  • 1st injection :
  • Ne 7.2 bar
  • 5 ms @ 0.47 s
  • 2nd injection : 52719
  • 80ms @ 0.6 s
  • Density, HXR increase
  • Faster ramp-down

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 10

pre-MGI vertical position

  • 53724: Z = 0.32m

midplane inj.

  • 53727: Z = 0.16m

top inj.

  • 53728: Z = 0.08m
  • inj. above plasma
  • Better Ne penetration with

MGI above midplane?

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 11

RE beam vertical position control

  • RE beam position control

Zmag = 32cm -> Zmag = 6cm

  • Better vertical control at

Zmag = 23cm

  • RE beam maintained to

Ip=20 kA

  • Record RE beam duration

tRE = 650 ms

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 12

Thomson Scattering System

  • Central region covered by new 5-channel spectrometers
  • Te measurements down to 5 eV
  • Top half of chamber covered by old 4-channel spectrometers
  • Te < 25 eV

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 13

TS raw data analysis

  • TCV Shot 53661 @ 1.4s
  • Te ≈ 5 eV

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 14

Conclusions

  • Reliable RE beam generation scenario
  • MGI in very-low density plasma
  • Full conversion of ohmic current to RE current
  • IOH control during RE beam phase
  • RE beam formation requires a significant amount of pre-MGI RE
  • Secondary MGI increases HXR and -dI/dt
  • Better Ne penetration with DMV aligned with plasma upper position
  • RE beam vertical control demonstrated
  • Better control at Z=23cm
  • RE beam maintained for 650ms without external drive (to Ip = 20kA)

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 15

2017 TCV RE experiment

  • New DMV above the plasma
  • REIS diagnostic for synchrotron radiation
  • Effect of plasma shaping on RE generation and mitigation
  • Feedback control of RE beam position and current
  • Effect of MGI composition, quantity, and position vs plasma
  • Bt scan

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 16

Extra slides

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 17

52717: Equil. reconstruction

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 18

MGI : effect of gas type

08.06.2017

  • J. Decker, et al. - REM 2017

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  • 52717 : Ne 7.2 bar
  • 5 ms @ 0.47 s
  • 52721 : Ar 2.0 bar
  • 20 ms @ 0.47 s
  • 52738 : Ar 17.7 bar
  • 2.5 ms @ 0.47 s
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SLIDE 19

Second MGI – Ne injection (2)

  • Z=0.16 m for 2nd injection
  • Slightly better gas

penetration?

08.06.2017

  • J. Decker, et al. - REM 2017

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SLIDE 20

52716 : RE loss events

08.06.2017

  • J. Decker, et al. - REM 2017

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