heating & current driving by lhw and ecw study on hl-2a

SW IP HL-2AHL-2A

Heating & Current Driving by LHW and ECW study on HL-2A

Bai Xingyu, HL-2A heating team

SW IP HL-2AHL-2AOutline

Introduction

EC experiments

ECCD experiments

ECRH experiments

Pre-ionization and Assisted Startup

LHCD experiments

LHCD &ECCD experiments

Summary

SW IP HL-2AHL-2AIntroduction

HL-2A is a normal

Tokamak device o

f China, located in

SWIP Chengdu Si

chuan Province. It

s main parameters：

Bt=2.7T, t=5s, R=1.65m, r=0.4m, Te=5keV, Ip=450kA,ne=6*1019m-3

HL-2M is on building


EC system：

68GHz :6*500kW gyrotrons2 antenna in 2 windowsRotatable mirror Duration 1s*4+1.5s*2

140GHz :2*1MW gyrotrons1 shared antennaRotatable mirrorDuration 3s

8 gyrotrons for ECRH


LH system：2*500kW klystrons2*12 antennan||=2.75

f=2.45GHz


Introduction

EC experiments

ECCD experiments

ECRH experiments


LHCD experiments


Summary

SW IP HL-2AHL-2AEC experiments

EC antenna structure of HL-2A

EC antenna (new)：

Rotatable in P direction:Lower 2 mirrors1MW/140GHz only

Rotatable in T direction:All mirrorsLeft for right & right for le

ft

SW IP HL-2AHL-2A

In ECRH condition, Ip=IOH+Ib+IEC

Where IOH=Vl / R

Vl is loop voltage

R is the plasma resistance

Ib≈cɛ1/2p Ip is Bootstrap current

c≈1/3 is proportionality constant

ɛ is the aspect radio

IEC is driving current

ECCD experiments

For the plasma is approximate constant,

R& p is constant

We know that IEC0=0 when EC is inject

ed in vertical direction

So the driving current in different direc

tion can be obtained by

IEC≈(1-cɛ1/2p)(Ip-Vl Ip0/Vl 0)

Where Ip0&Vl 0 are separately plasma c

urrent and loop voltage in vertical i

njection condition

SW IP HL-2AHL-2AECCD experiments Shot Φ

(degree)dIOH/dt (kA/

s)IEC(kA) EC(1019A

m-2W-1)

20104 -8 -10.534 -11.91 0.098

20105 -6 -11.402 -25.66 0.122

20106 -4 -10.149 -5.813 0.033

20107 0 -9.782 0 0

20108 -10 -10.51 -11.53 0.08

ECCD efficiency

has an optimized

inject angle

SW IP HL-2AHL-2AECRH experiments

H mode is obtained for the first time on H

L-2A in 2009 （ shot 11333）H mode can be obtained by ECRH and N

BI or only NBI on HL-2APEC=1.62MW， PNBI=0.26MW (22151)

NBI power is much less than the H mode threshold

(MIN NBI power is 570kW for L-H transition)

The output power of EC system (3MW/68GHz) can r

each 2.5MW

Can H mode be obtained only by ECRH ?

ECRHNBI


ECRH-H modeW7-AS[V. Erckmann, PRL1993]0.45MW/140GHz/X2

DIII-D[J. Lohr, PRL1988]60GHz/0.9MW/X2 r/a - 0~0.3

ASDEX-U[F. Ryter, NF2009]140GHz/>1.3MW/X2 r/a=0~0.3

SW IP HL-2AHL-2AECRH experiments SMBI makes ne increase rapidly. limit cycle oscillation

(LCO) appears in the following ne-decrease section

Conditions:

• Siliconized wall

• Ne is controlled above 1.5 by SMBI

• Displacement and X point angle control

• Bt=1.34， inject point r/a=0.45

• ECRH power1.5MW

Long SMBI


LCO phenomenon with ELMs feature 22909 NBI H-mode

23065

1kHz

Bt~1.31T, r/a~0.3, PECRH ~1.6MW

During ECRH， the displacement is c

ontrolled minus to avoid cutting off. Ne i

s feedback controlled 1.75 by SMBI.

LCO frequency is 2-3kHz. Once (700ms

~800ms) 1kHz component appears. And t

he oscillation waveform has ELMs featur

e


Pump out phenomenon:

Ne decreases while ECRH

power increases and remain

stable at a certain value. In

the new profile, ne

decreases in core and

increases on the edge. Ne

profile is changed from

peaking to hollow

NBIECRH

In the ECRH H mode

experiments, pump out

phenomenon is a big

problem

ECRH Te↑

ne ↓

Power threshold ↑

electron-ion collision rate↓

Ti ↓

Harder L-H transition

SW IP HL-2AHL-2APre-ionization & Assisted Startup

On HL-2A, in order to build up scenarios for ECRH pre-ionization and assisted startup

to relax the conditions required to breakdown and startup plasma on HL-2M, and

to clarify the ITPA IOS2.3 open issue, ECRH pre-ionization and assisted startup experim

ents have been carried out during 2010, 2011 and 2012 experiment campaigns


Waveform for min ECRH power and pure ohmic start up

Min breakdown voltage ： 0.5V Toroidal Electric field ： 0.05V/m ( 1/6 ITER value)Tt is the smallest value ever obtained by TokamakMin breakdown voltage of ohmic: 3.4VThe minimum breakdown voltage was reduced much

SW IP HL-2AHL-2AITPA IOS2.3 open issue

The earlier application of loop voltage does not delay or hinder the av

alanche formation on HL-2A, and even better than that of later appli

cation of loop voltage. There is no problem for earlier application of l

oop voltage.

Why shorter delay times for earlier application? Loop voltage may accelerate t

he initial free electrons (about 0.03 eV) to a higher energy value close to subcri

tical energy, so the X2 mode absorption rate become higher, which causes the e

arlier breakdown.


Shot: 14444O1-modeP=200kWt=108ms, 117ms

Shot: 16289X2-modeP=600kWt=108ms, 117msangle 0°,

Shot: 16617X2-modeP=800kWt=126ms, 135msangle 20°

The minimum ECRH powers

O1- mode： 200kW

X2- mode： 300kW

Parameter influence

wall condition

prefilled gas pressure

field null structure

toroidal injection angle


Introduction

EC experiments

ECCD experiments

ECRH experiments


LHCD experiments


Summary

SW IP HL-2AHL-2A

In LHCD condition, Ip=IOH+Ib+ILH

Where IOH=Vl / R

While without LHCD, Ip0=IOH0+ Ib0

For the plasma current is feed back controlled, Ip should be the same as that

without LHCD. Ib is considered to be constant and small (less than 10% Ip )

Ip = Ip0, Ib = Ib0 , Ip ≈ IOH=Vl / R,

So, ILH=IOH0-IOH

Which means

ILH ≈ Ip ΔVl /Vl

But the fact is a little more complex. Ip is not controlled completely.

LHCD experiments

SW IP HL-2AHL-2ALHCD experiments

ILH is formed by 2 components:

ILH =IΔVl + ΔIp

Where ΔIp can be read from data

Typical LHCD result on HL-2A

SW IP HL-2AHL-2ALHCD experiments

ShotLHCD power（ kW）

LH

(1019Am-2W-1)

RC（%）

limiter（ cm）

Ne

(1019m-3)

9751 57.5 0.085 30.6 39 1.1

9752 57 0.094 28.9 39 1.8

9763 89.8 0.013 15.5 38 0.9

9771 95.8 0.059 36.4 38 0.86

9772 95.1 0.062 35.8 38 0.92

9773 101.2 0.033 37 38 1.85

9778 123.1 0.032 23.2 38 0.84

9782 119.2 0.077 26.8 38 0.57

9788 92.5 0.155 29.8 38 1.45

9789 92.2 0.254 36.3 38 0.91

9790 95.1 0.171 36.3 38 0.82

9791 93.5 0.181 35.7 38 0.95

9964 48.4 0.01 20.3 38 0.56

9965 39.3 0.05 35.1 38 0.6

LHCD efficiency on HL-2A


Introduction

EC experiments

ECCD experiments

ECRH experiments


LHCD experiments


Summary

SW IP HL-2AHL-2ALHCD &ECCD experiments

Full CD obtained by LHCD&ECCD

shot RC（%） With ECCD

9771 36.4 NO

9772 35.8 NO

9773 37 NO

9774 34.2 YES

9775 28.2 YES

9776 25.1 YES

9777 22.3 YES

9778 23.2 YES

9779 Ip disturb YES

9780 Ip disturb YES

9781 26.2 YES

9782 26.8 YES

ECCD improve absorption of LHW

Why ECCD can improve LHW absorption？Pump out phenomenon makes particle move out,

which increase edge density. That form a puffi

ng gas effect on the edge, which make LHW co

upling better.


Introduction

EC experiments

ECCD experiments

ECRH experiments


LHCD experiments


Summary

SW IP HL-2AHL-2ASummary

EC experiments was carried out on HL-2AECCD efficiency was estimated and compared with theory

H mode experiments by ECRH only was tried. LCO phenomenon with ELMs f

eature was obtained

Pre-ionization and assisted startup experiment by ECW was carried out. The s

mallest Toroidal electric field ever in Tokamak is obtained. The result shows that

earlier application of loop voltage does not delay or hinder the avalanche formati

on, even better, which solves ITPA IOS2.3 open issue

LHCD experiments was carried out on HL-2ALHCD efficiency was estimated

LHCD &ECCD experiments was carried out alsoFull CD was observed

ECCD improve LHCD coupling phenomenon was achieved and analyzed

SW IP HL-2AHL-2A

heating & current driving by lhw and ecw study on hl-2a

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