hl-2a lisboa, portugal 22 to 24 october, 2007 dong yunbo recent experiment results during electron...

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HL-2A

Lisboa, Portugal 22 to 24 October, 2007 Dong Yunbo

Recent Experiment Results Recent Experiment Results during electron cyclotron during electron cyclotron

heating on HL-2Aheating 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

17th IAEA Technical Meeting on Research Using Small Fusion Devices

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HL-2A


OutlineOutline 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

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HL-2A


ECRH experiment on HL-2A








OutlineOutline

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HL-2A


HL-2A Tokamak

Physics issues on HL-2APhysics issues on HL-2A Transport: thermal transport, particle transport, im

purity transport, … SOL and divertor: Edge and pedestal physics: MHD and disruptions: NTM, ELMs, TAEs, … Turbulence: Zonal Flows Confinement and advanced scenarios: H-mode, …

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

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HL-2A


Layout of HL-2A Tokamak

SMBISMBIPellet InjectionPellet Injection

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

1.5MW/1.5MW/50keV/2sNBI 50keV/2sNBI systemsystem

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

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

Thomson Thomson ScatteringScattering

CXRSCXRS

8-Channel HCN 8-Channel HCN interferometerinterferometer

VUV spectrometerVUV spectrometer

MW reflectometerMW reflectometer

ECEECE

Fast scan probesFast scan probes

Neutral Neutral Particle Particle AnalyzerAnalyzer

SDD soft X ray SDD soft X ray spectrumspectrum

Bolometer & Soft X ray Bolometer & Soft X ray arraysarrays

Other Diagnostics, … …Other Diagnostics, … …

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HL-2A


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)

ECRH systerm

Transmission line

corrugated waveguide, miterbends, DC breaks;

Launcher

focusing mirrors, steering mirrors;

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HL-2A


r/a = 0r/a = 0

r/a = 0.4r/a = 0.4

Te increasing

Density pump-off

Radiation increasing

H alpha inceasing

ECRH

Radiation increasing

ECH experiments

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HL-2A


ECRH experiment on HL-2A








OutlineOutline

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HL-2A


SMBI on HL-2A

The SMBI with clusters may be of benefit for deeper fuelling

Stair-shaped density increments

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

H2 inlet

CCD Camera

SMB Valve

Hα Array 1

Hα Array 2

Separatrix

Lower divertor

Target plate

LN2 output

LN2 inlet

Turbo Pump

Arrangement for SMBI in the HL-2AGas pressure: 1 M Pa to 3 M PaPulse duration of Jet : 2 msPulse interval: 50 ms to 100 ms

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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.


Gas pressure of D2: 2.0 MPaPulse number: 10, later 5 pulses during ECRHPulse duration: 0.3 msPulse interval: 50 msECRH Power: 1034 kWECRH duration: from 800 ms to 1200 ms

neutron account

spring

Laval nozzle

valve

piston

inlet outlet

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.

SMB Injector

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high field side

Ha and radiation losses drop （ Enhanced energy confinement ）


15

q=2q=2

(PECRH = 800 kW, TSMBI = 810 ms)

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.

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HL-2A


Non-local transport phenomena

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

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.

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Steep SX profile

Te increase


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Delayed Te decrease

Off-axis ECRH

0

20

40

60

15 17 19 21 23 25 27

r( cm)

Xe(c

m2/m

s)

OHECRHj ust af ter ECRH

Power deposition location

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.

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HL-2A



Steep SX profile

Nearly unchanged Te0

ne increase slightly

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

Possible explanation:

Larger sawtooth

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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.

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

(b) off-axis ECH (PECH=340kW)

20

normal

larger

smaller

double

saturated

giant

hill

humpback

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HL-2A


Non-standard sawtooth during ECRH

Double Sawtooth

Compound(saturated+double)Sawtooth

m=1 islandSVD

m=1islandSVD

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HL-2A

Lisboa, Portugal 22 to 24 October, 2007 Dong Yunbo 22

•Heating effect during crash or reconnection

Possible explanation:

hills humpback

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

Non-standard sawtooth during ECRH

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HL-2A


axisq=1 surface

25

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.

Stabilization of sawtooth activity–giant sawtooth

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.

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.

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Fast particle driven instabilities: Fishbones

Low field side deposition PECRH =650kW

High field side deposition PECRH=280kW

•0.4

•0.5

• f（kHz）

•wavelet spectrum

•700 •705 •710 •715 •720 •725 •730

•5

•15

•20

•10

Fishbone like instabilities

Crash

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

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Lisboa, Portugal 22 to 24 October, 2007 Dong Yunbo 32

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

0.0 0.2 0.4 0.6 0.8 1.0

-0.4

-0.2

0.0

0.2

s=-0.1 s=-0.02 s=0 s=0.02 s=0.1

Gc

k

Normalized precession velocity of circulating electrons

30 – 60 keV

10 –30 keV

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HL-2A


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

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Thank you Thank you for attention!for attention!

hl-2a lisboa, portugal 22 to 24 october, 2007 dong yunbo recent experiment results during electron...

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