Overview of HL-2A Experiment Results

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Overview of HL-2A Experiment Results
Qingwei YANG for HL-2A Team
SouthWestern Institute of Physics, Chengdu, China
Cooperated with University of Science and
Technology of China, Hefei, China Institute of
Plasma Physics, Chinese Academy of Sciences,
Hefei, China Institute of Physics, Chinese
Academy of Sciences, Beijing, China Tsinghua
University, Beijing, China   MPI für
Plasmaphysik, Association Euratom,
GermanAssociation Euratom-CEA, CEN Cadarache,
France GA, San Diego, USA NIFS, Toki, Japan JAEA,
Naka, Japan Kurchatov Institute, Russia
21th IAEA Fusion Energy Conference, Oct. 1622,
2006, Chengdu, China
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Outline

• Introduction
• Operation regime
• Physics studies
• Summary and future plan

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Introduction Since the last IAEA Fusion Energy
Conference in 2004, the plasma parameters of the
HL-2A tokamak have been increased significantly
with the improvement of the hardware. The stable
and reproducible discharges with divertor
configuration have been obtained by reliable
feedback control and wall conditioning
techniques. Up to now, the main plasma
parameters are as follows

• BT 2.8 T 2.7 T
• IP 480 kA 400 kA
• Duration 3.0 s
• Plasma density 6.0 x 1019 m-3
• Electron temp. gt 2.0 keV
• Ion temperature gt 800 eV
• Fuelling sys. GP, SMBI, PI
• Heating sys. ECRH, LHCD, NBI

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ECE
CXRS
8-Channel HCN interferometer
MW reflectometer
Thomson Scattering
VUV spectrometer
Bolometer Soft X ray arrays
SDD soft X ray spectrum
Fast scan probes
Neutral Particle Analyzer
Other Diagnostics,
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Operation regime

• The sustained divertor discharges are achieved by
  reliable feedback control. The low single null
  divertor is the usually used configuration on
  HL-2A.
• The high density discharges are obtained by
  gas-puffing, SMBI and PI.
• The Greenwald limit can be exceeded.

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Outline

• Introduction
• Operation regime
• Physics studies
• Summary and future plan

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Liquid nitrogen temperature SMBI

• Supersonic molecular beam injection (SMBI) system
  with gas pressure of 0.23.0 MPa and LN
  temperature
• A cluster contains about 250 hydrogen atoms (in
  average) at pressure of 1.0 MPa in this
  measurements
• The cold molecular beam (LN temperature) can
  penetrate into plasma deeply
• The MBI with clusters may be of benefit for
  deeper fuelling

• L.H.Yao, et al., this conf., EX/P3-21.

SRS intensity of Rayleigh scattering
Room Temp.LN Temp.
center
edge
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Penetration depth scaling of SMBI

• The penetration depth is studied with FFT
  analysis of modulated injection and tangential
  H-alpha array to detect the penetration depth.
• The penetration depth (working gas is at room
  temperature) is dependent on the plasma
  parameters and pressure of working gas.
• Asymmetric penetration using SMBI is observed in
  low density ( 11019m-3) by ECE and soft X- ray.
  The penetration depth is about 30 cm from the low
  field side (LFS) and only about 10 cm from the
  high field side (HFS).

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Particle transport analysis with modulated MBI

• Formula used
• The particle diffusion coefficient on the Ohmic
  discharge is about 0.5 1.5m2/s at r/a 0.6
  0.75.
• It is about 1/4 of the electron heat diffusivity.

• Particle transport is studied with modulated SMBI
  and microwave reflectometer.
• After the FFT, the amplitude and the phase
  profiles of the first harmonic and high harmonics
  can be obtained.

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Study of toroidal symmetry of GAM ZFs (1)

• A novel design of three-step Langmuir probes is
  developed for ZF detection.
• The radial component of electric field and
  gradient of Er
• The poloidal and toroidal coherencies of electric
  potential can be calculated using F1F6, and
  F1F11, respectively.

• To explore the generation mechanism of the GAM
  ZFs, squared cross-bicoherence is calculated

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Study of toroidal symmetry of GAM ZFs (2)

• Toroidal symmetry (n 0) of the GAM zonal flow
  in a tokamak is identified for the first time.
• 3-D spatial features of the GAM ZFs are analyzed,
  simultaneously.
• Nonlinear three wave coupling is identified to be
  a plausible physical mechanism for the generation
  of the GAM ZFs.
• Studies of interactions between the ZFs and the
  ambient turbulences are in progress.

• K.J.Zhao, et al., Physical Review Letters, 96
  (2006), 255004
• L.W.Yan, et al., this conf., EX/P4-35.

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Confinement improvement after pelIet injection

• The q profile is reconstructed with TRANSP code
  using experimental data
• The weak magnetic shear is achieved after PI
• The improved confinement sustains about 500 ms

Te/Ti 1
Te/Ti 1.5

• ?e in plasma peripheral decreases after PI
• Evidence of confinement time dependence of Te/Ti
  is observed

• X.T.Ding, et al., Chin. Phys. Lett. Vol.23
  (2006), 2502.

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Investigation of impurity transport with LBO

• Al and Ti are injected into plasma using laser
  blow-off.
• the transport of impurity in plasma center is
  slower than that in the outer region.
• The transient asymmetric profile, inward
  transport and outward diffusion are observed
  using tomography of the soft X ray radiation.
• D 0.5 1.0 m2/s, V 1 10 m/s at 0.2 lt r/a lt 0.8

• Z.Y.Cui, Y.Huang, P.Sun, et al., Chin. Phys.
  Lett. Vol.23 (2006), 2143.

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Statistic analysis of disruption

• Most of the plasma current quench time is 46 ms
  in the major disruptions.
• The induced loop-voltage is proportional to the
  current quench rate.
• The disruption regime in the dIP0/Stq/S plane is
  identified.
• A new parameter, , is introduced to
  predict disruption. The physical meaning of this
  parameter is the amplitude multiplies the period
  of MHD perturbation.
• The disruption mitigation by noble gas (Neon and
  Argon) puffing are demonstrated.

HL-2A
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Sawtooth behaviours in ECRH experiment

• The saturated sawtooth and strong m 1 precursor
  is found during on-axis ECRH.
• The period of sawtooth decreases during on-axis
  ECRH discharges
• The heat transport increases in on-axis ECRH
  discharges

• Yi Liu, et al., this conf., EX/P8-13

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Coupling between m 1 and m 2 oscillation

• A large, persistent m 1 perturbation of snake
  structure is observed in sawtooth free plasma
  after PI (or SMBI).
• This m 1 mode is detected by soft X ray arrays,
  but not detected by Mirnov coils.
• An m 2 magnetic perturbation with the same
  frequency is observed during the decay of m 1
  mode.

Freq. kHz
10
0
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Detached divertor is observed

• In experiment, the phenomenon similar to the
  partially detached divertor regime is observed
  with ne 1.51019m-3 in main plasma.
• Numerical analysis of HL-2A divertor discharges
  is done using SOLPS 5.0 code.
• It is the linear regime at ne
  0.51019m-3Detached phenomenon appears at
  21019m-3 ne 31019m-3
• The reason for the easy detachment may be the
  long divertor legs and thin divertor throats.

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Summary and future plan (1)

• The detailed investigations of SMBI are carried
  out. A penetration depth scaling is revealed. The
  LNT SMBI can penetrate into plasma more deep. The
  MBI with clusters may be of benefit for deeper
  fuelling The penetration depth of SMBI is much
  deeper in LFS than in HFS at low density
  discharges.
• The particle diffusion coefficient is about
  0.51.5m2/s in plasma peripheral region, using
  microwave reflectometer and modulated SMBI.
• 3-D features of GAM ZFs are determined with novel
  designed 3-step Langmuir probes. The symmetries
  (m01, n 0) of the directly measured low
  frequency (79 kHz) electric potential and field
  are simultaneously observed.
• The diffusion coefficient D and convection
  velocity V of impurity are fitted using LBO D
  0.51.0 m2/s, V 1 10 m/s.
• A new parameter is introduced to predict the
  disruption. The noble gas injection successfully
  increase the current quench time from 5 ms to
  longer than 20 ms.
• A large, persistent m 1 perturbation of snake
  structure is observed in sawtooth free plasma
  after PI (or SMBI). An m 2 magnetic
  perturbation with the same frequency is induced
  by the m 1 mode.
• The detached (or partially detached) divertor
  regime is easily occurrence, even in the
  intermediate density operation. The reason may be
  the long divertor legs and thin divertor throats.
  The numerical simulations are in good agreement
  with the experiments.

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Summary and future plan (2)

• H - mode operation and physics
• Realizing the H-mode discharge by ECRH
• Pedestal physics studies
• High Beta operation
• Confinement
• Impurity, particle transport, thermal transport
• Synergy of ECCD LHCD using 2 MW ECCD and 1MW
  LHCD
• Disruption control
• Disruption prediction, Disruption mitigation by
  SMBI
• Zonal flows studies of low-frequency ZFs
• MHD instabilities
• Seed island/sawteeth control
• Mode coupling studies
• Investigation of ELMs in H-mode discharges
• Divertor physics

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Thanks for your attention