Recent experiment results during electron cyclotron heating on hl 2a
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17 th IAEA Technical Meeting on Research Using Small Fusion Devices. Recent Experiment Results during electron cyclotron heating on HL-2A. Y.B.Dong, Y.Liu, H.J.Sun, W. Chen, W.W.Xiao, J. Zhou, W. Deng, L.H.Yao, B.B.Feng, J.Rao , Q.W.Yang , X.T.Ding , Yong Liu , and C.H.Pan

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Recent Experiment Results during electron cyclotron heating on HL-2A

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Recent experiment results during electron cyclotron heating on hl 2a

17th IAEA Technical Meeting on Research Using Small Fusion Devices

Recent Experiment Results during electron cyclotron heating on HL-2A

Y.B.Dong, Y.Liu, H.J.Sun, W. Chen, W.W.Xiao, J. Zhou, W. Deng, L.H.Yao, B.B.Feng, J.Rao , Q.W.Yang , X.T.Ding , Yong Liu , and C.H.Pan

E-mail of main author: [email protected]

Southwestern Institute of Physics (SWIP), Chengdu, China


Recent experiment results during electron cyclotron heating on hl 2a

Outline

  • ECRH experiment on HL-2A

  • Experiment results on HL-2A

    • Confinement enhancement by SMBI during ECRH

    • Non-local transport phenomena induced by SMBI

    • Reduced core transport after ECRH switch-off

    • Sawtooth behaviour during ECRH

    • Exiting of the m=1/n=1 mode during ECRH

  • Future plan in ECRH/CD experimenton HL-2A


Recent experiment results during electron cyclotron heating on hl 2a

Outline

  • ECRH experiment on HL-2A

  • Experiment results on HL-2A

    • Confinement enhancement by SMBI during ECRH

    • Non-local transport phenomena induced by SMBI

    • Reduced core transport after ECRH switch-off

    • Sawtooth behaviour during ECRH

    • Exiting of the m=1/n=1 mode during ECRH

  • Future plan in ECRH/CD experimenton HL-2A


Recent experiment results during electron cyclotron heating on hl 2a

HL-2A Tokamak

  • Main parameters of HL-2A

  • Major radius:1.65 m

  • Minor radius:0.40 m

  • Toroidal field:2.8 T-3.5T

  • Plasma current:480 kA

  • Magnetic flux:5.0 Vs

  • Discharge duration:1.5 sec.

  • Plasma density: 4.2 x 1019 m-3

  • Electron temperature: 5.0k eV

  • Ion temperature:600 eV

  • Physics issues on HL-2A

  • Transport: thermal transport, particle transport, impurity transport, …

  • SOL and divertor:

  • Edge and pedestal physics:

  • MHD and disruptions: NTM, ELMs, TAEs, …

  • Turbulence: Zonal Flows

  • Confinement and advanced scenarios: H-mode, …


Recent experiment results during electron cyclotron heating on hl 2a

1.5MW/50keV/2sNBI system

SMBIPellet Injection

ECE

CXRS

2*500kW /1s /68GHz ECRH/ECCD

8-Channel HCN interferometer

MW reflectometer

Thomson Scattering

VUV spectrometer

Bolometer & Soft X ray arrays

SDD soft X ray spectrum

2*500kW /1S /2.45GHz LHCD system

Fast scan probes

Neutral Particle Analyzer

2*500kW/1s /68GHz ECRH/ECCD

Other Diagnostics, … …

Layout of HL-2A Tokamak


Recent experiment results during electron cyclotron heating on hl 2a

ECRH systerm

  • The fundamental O-mode EC wave with the wide steering angles in poloidal (~25º) and toroidal (~25º) directions

  • The ECW launched from 2 equatorial ports, 4 gyrotrons

  • The maximum power is 2 MW (1.7 MW in experiments)

Transmission line

corrugated waveguide, miterbends, DC breaks;

Launcher

focusing mirrors, steering mirrors;


Recent experiment results during electron cyclotron heating on hl 2a

ECRH

Radiation increasing

r/a = 0

H alpha inceasing

Density pump-off

r/a = 0.4

Radiation increasing

ECH experiments

Te increasing


Recent experiment results during electron cyclotron heating on hl 2a

Outline

  • ECRH experiment on HL-2A

  • Experiment results on HL-2A

    • Confinement enhancement by SMBI during ECRH

    • Non-local transport phenomena induced by SMBI

    • Reduced core transport after ECRH switch-off

    • Sawtooth behaviour during ECRH

    • Exiting of the m=1/n=1 mode during ECRH

  • Future plan in ECRH/CD experimenton HL-2A


Recent experiment results during electron cyclotron heating on hl 2a

Target plate

Separatrix

Hα Array 1

LN2 output

SMB Valve

H2 inlet

LN2 inlet

Turbo Pump

CCD Camera

Hα Array 2

Lower divertor

SMBI on HL-2A

  • The SMBI with clusters may be of benefit for deeper fuelling

Stair-shaped density increments

  • Arrangement for SMBI in the HL-2A

  • Gas pressure: 1 M Pa to 3 M Pa

  • Pulse duration of Jet : 2 ms

  • Pulse interval: 50 ms to 100 ms

The plasma density increases after MBI, while a temperature drop was observed in the central ECE channel.


Confinement enhancement by smbi during ecrh

During ECRH a series pulse SMBI fueling, the plasma storage energy WE, Beta_p, line averaged density ne and “fusion neutron” account increase, the plasma confinement was improved.

spring

Laval nozzle

valve

piston

neutron account

outlet

inlet

Confinement enhancement by SMBI during ECRH

SMB Injector

A new pneumatic supersonic molecular beam injector is developing to realize the SMBI from HFS, which will be beneficial to deeper injection and higher fuelling efficiency.

Gas pressure of D2: 2.0 MPa

Pulse number: 10, later 5 pulses during ECRH

Pulse duration: 0.3 ms

Pulse interval: 50 ms

ECRH Power: 1034 kW

ECRH duration: from 800 ms to 1200 ms


Recent experiment results during electron cyclotron heating on hl 2a

Outline

  • ECRH experiment on HL-2A

  • Experiment results on HL-2A

    • Confinement enhancement by SMBI during ECRH

    • Non-local transport phenomena induced by SMBI

    • Reduced core transport after ECRH switch-off

    • Sawtooth behaviour during ECRH

    • Exiting of the m=1/n=1 mode during ECRH

  • Future plan in ECRH/CD experiment on HL-2A


High field side

q=2

q=2

Non-local transport phenomena induced by SMBI

high field side

(PECRH = 800 kW, TSMBI = 810 ms)

  • Ha and radiation losses drop(Enhanced energy confinement)

After the injection of SMB, outside r~20cm the plasma is cooled while the core Te increase. A steep Te profile in the plasma core is sustained for about 40ms. Meanwhile the radiation of bolometer and Ha decrease.

15


Recent experiment results during electron cyclotron heating on hl 2a

Non-local transport phenomena

The non-local effect appears after the injection of the latter two SMBs during ECRH and OH, while the first one doesn’t induce such an effect. The effect always occurs with low density and the density limit is larger during ECRH.

  • Happened in low density range(ne~1-2x1013cm-3)

  • Located between q=1 and q=2 surface

  • Central temperature increase of 200ev

  • Duration of the process is longer: the effect lasts about 5ms in RTP, it is about 40ms in HL-2A

  • Radiation of bolometer and Ha decrease in HL-2A, there is no sign of the decrease in RTP


Recent experiment results during electron cyclotron heating on hl 2a

Outline

  • ECRH experiment on HL-2A

  • Experiment results on HL-2A

    • Confinement enhancement by SMBI during ECRH

    • Non-local transport phenomena induced by SMBI

    • Reduced core transport after ECRH switch-off

    • Sawtooth behaviour during ECRH

    • Exiting of the m=1/n=1 mode during ECRH

  • Future plan in ECRH/CD experimenton HL-2A


Recent experiment results during electron cyclotron heating on hl 2a

Off-axis ECRH

Delayed Te decrease

Power deposition location

Te increase

Reduced core transport after ECRH switch-off

Steep SX profile

The central Isx remains constant for some times after ECRH switch off, while the off-axis Isx decrease, ▽Te increase and the transport coefficients reduce.

23


Recent experiment results during electron cyclotron heating on hl 2a

Larger sawtooth

Possible explanation:

ne increase slightly

Reduced core transport after ECRH switch-off

Nearly unchanged Te0

Steep SX profile

Off-axis ECRH switch-off leads to current density redistribution and transiently low shear, causing a local confinement improvement.


Recent experiment results during electron cyclotron heating on hl 2a

Outline

  • ECRH experiment on HL-2A

  • Experiment results on HL-2A

    • Confinement enhancement by SMBI during ECRH

    • Non-local transport phenomena induced by SMBI

    • Reduced core transport after ECRH switch-off

    • Sawtooth behaviour during ECRH

    • Exiting of the m=1/n=1 mode during ECRH

  • Future plan in ECRH/CD experiment on HL-2A


Recent experiment results during electron cyclotron heating on hl 2a

normal

(b) off-axis ECH

(PECH=340kW)

(a) on-axis ECH ( PECH=450kW);

larger

smaller

giant

double

saturated

hill

humpback

Sawtooth behaviour during ECRH

  • The auxiliary heating power is up to 2MW in the ECRH experiment of HL-2A tokamak.

  • on-axis ECH (with a more peaked profile)

  • off-axis ECH (with flat profile, no “hot ears”)

A sawtooth tends to saturate or decrease in its ramp phase, and the sawtooth shape is usually changed, leading to formation of a saturated sawtooth, a compound sawtooth, a humpback or a hill.

20


Recent experiment results during electron cyclotron heating on hl 2a

SVD

m=1 island

SVD

m=1island

Non-standard sawtooth during ECRH

  • Double Sawtooth

  • Compound(saturated+double)Sawtooth

21


Recent experiment results during electron cyclotron heating on hl 2a

Possible explanation:

Non-standard sawtooth during ECRH

hills

humpback

The Te growth in both case corresponds to some temporary improvement of the global confinement

  • Heating effect during crash or reconnection

22


Recent experiment results during electron cyclotron heating on hl 2a

Stabilization of sawtooth activity–giant sawtooth

The most significant response to a change in the heating location is the rapid change in sawtooth shape and period as the heating location crosses the inversion surface.

Large sawtooth: PECRH=1393kW, Bt=2.24T, r’=-14cm, Ne=2.4×1019m-3, rq=1=12cm(obtained from SVD),deposion location is just outside the q=1 surface.

q=1 surface

axis

Ne=2.0×1019m-3, Pecrh=1100kW, rq=1 = 11cm,

The maximum sawtooth period is obtained for power deposition close to the HFS q=1 surface, located at 9.8cm. The sawtooth periods are smaller near the axis.

25


Recent experiment results during electron cyclotron heating on hl 2a

Outline

  • ECRH experiment on HL-2A

  • Experiment results on HL-2A

    • Confinement enhancement by SMBI during ECRH

    • Non-local transport phenomena induced by SMBI

    • Reduced core transport after ECRH switch-off

    • Sawtooth behaviour during ECRH

    • Exiting of the m=1/n=1 mode during ECRH

  • Future plan in ECRH/CD experiment on HL-2A


Recent experiment results during electron cyclotron heating on hl 2a

Crash

Fishbone like instabilities

  • 20

  • 15

  • 10

  • f(kHz)

  • 5

  • 705

  • 710

  • 715

  • 720

  • 725

  • 730

  • 700

  • wavelet spectrum

  • 0.5

  • 0.4

Fast particle driven instabilities: Fishbones

Low field side deposition PECRH =650kW

m=1/n=1 “fishbone like instaility” exited with

  • Electron density < 3x1013cm-3

  • Power of ECRH < 900kW

  • Both high field side and low field side deposition

High field side deposition PECRH=280kW


Recent experiment results during electron cyclotron heating on hl 2a

30 – 60 keV

10 –30 keV

Normalized precession velocity of circulating electrons

Destabilizing effect of suprathermal electrons

Increase of hard X ray during ECRH

  • Electron fishbone excited by the barely trapped electrons(Procession reversal )

    (Ding X.T,Liu Yi,Nuclear Fusion Vol.42,No5(2002)491)

  • Electron fishbone excited by the circulating electrons

    Z.T.Wang,Nuclear Fusion47

32


Recent experiment results during electron cyclotron heating on hl 2a

Future plan in ECRH/CD experiment on HL-2A

Future plan in ECRH/CD experimenton HL-2A

  • Confinement enhancement with ECRH ( H-mode )

  • Transport study with ECRH

    • ITB formation;

    • Non-local transport phenomena

    • Electron heat transport and ECRH modulation experiments

  • MHD study with ECRH/CD

    • Correlation between MHD activities and ITB emergence

    • Control of NTM mode by controlling of sawtooth period

    • Exiting of the e-fishbone during ECRH

46


Recent experiment results during electron cyclotron heating on hl 2a

Thank you for attention!


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