fundamental x-mode electron cyclotron current drive

Fundamental X-mode Electron Cyclotron Current Drive using Remote-Steering Symmetric Direction Antenna

at Larger Steering Angles

H. Idei1, K. Hanada1, H. Zushi1, K. Ohkubo2, M. Hasegawa1, S. Kubo2, K. N. Sato1, K. Nakamura1, M. Sakamoto1, A. Iyomasa1, S. Kawasaki1, H. Nakashima1, A.Higashijima1, T. Notake3, T .Shimozuma2, S. Ito2, H. Hoshika4, N. Maezono4, S. Nishi4, K. Nakashima4

and TRIAM Experimental. Group1

1 Research Institute for Applied Mechanics, Kyushu University, Kasuga, 816-8580, Japan 2 National Institute for Fusion Science, Toki, 509-5292, Japan

3 Faculty of Engineering, Nagoya University, Nagoya, 464-8603, Japan 4Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga,

816-8580, Japan

The 20th IAEA Conference, PD/1-2 H. Idei et al.

OutlineTRIAM, Advanced Fusion Research Center

1. Introduction Remote Steering Antenna relevant to ITER Application New Hardware on ECH/ECCD after the 19th IAEA in TRIAM-1M

2. Symmetric Direction Remote Steering Antenna with Larger Steering Angles Output Beam Pattern ---- Gaussian Content ---- Output Steering Angle [ based on Intensity & Phase Measurements ] Transmission Efficiency

3. ECH / ECCD Experiments on the TRIAM-1M tokamak Mode Purity Control Experiment O-mode Experiment X-mode Experiment

4. Summary


Remote Steering Antenna with Symmetric- and Asymmetric- Angles

Asymmetric

direction

a

a

L

Symmetric

direction

TRIAM, Advanced Fusion Research Center

f : 170GHza : 31.75mm

Transmission efficiency = P out / P in

: perpendicular field to steering planeE

(K.Ohkubo)

Dependence of Transmission Efficiency on and L

[imaging property in fundamental mode]

20

10

00.0 0.5 1.0 1.5 2.0 2.5 3.0

L[m]

[deg.]

20

10

00.0 0.5 1.0 1.5 2.0 2.5 3.0

L[m]

Extended Steering Capability

0.0

0.2

0.4

0.6

0.8

1.0

0 5 10 15 20

Tra

nsm

issi

on E

ffic

ienc

y

Steering Angle [ degrees ]

L=2.245mAsymmetric

Normal Branch

L=2.075mSymmetric Extended Branch

Larger Steering Angles

[ near 0 degree ][ 8-19 degrees ]

Asymmetric[ITER]

Symmetric[TRIAM]


ECH/ECCD System in TRIAM-1M tokamakTRIAM, Advanced Fusion Research Center

Operating Frequency : 170GHz : Magnetic Field ~ 6T. Heating Scenario : Fundamental O/X-mode from Low Field side

ITER Condition

N//, v//

WaterDummy Load

Gyrotron MOU forAntenna

MOU

Gate Valve

BrickDummy Load

Polarizer Polarizer

Remote Steering Antenna

[200kW:5s]

After 19th IAEA

Steering Angle in

B, Ip


Antenna System for the TRIAM-1M tokamak TRIAM, Advanced Fusion Research Center

Gate Valve

Antenna

DifferentialPumping Port

EvacuatedWaveguide Line

5

10

15

20

25

30

0 200 400 600 800 1000 1200

beam

siz

e [m

m]

propagation position z (mm)

M1 M2

M3

M4

M1

M2 M3

M4 SteeringMirror

Matching Optics Unit for Antenna

M1

M2 M3

M4

Square CorrugatedWaveguide Antenna( Remote SteeringAntenna )

Remote Steering Antenna



0.00

0.05

0.10

0.15

0.20

-5

0

5

10

15

20

25

30

-20-10 0 10 20 30 40 50 60

Inte

nsity

[ a

.u. ]

Phas

e [

radi

an ]

x [ mm ]

x=11mm

Rx=

218mmThe phase rapidly changes near the side lobe, therefore, the side lobe part is spread out from the main lobe along the propagation.

[ Ey Component: 15 degree steering case ]

Output Beam Analysis [ Output pattern & Steering Angle ]

Output Beam is analyzed using Moment Method to evaluate the beam center offset and the steering angle, and using Matching Coefficient to evaluate Gaussian Content.

The phase profile is flat near the beam center.The beam propagates along the measuring z-axis.

x

yz

15 degrees



Analysis by Moment Method & Matching Coefficient

The n-th moment in the x direction is defined with the amplitude distribution A(x, y) as,

The dependence of the beam center position on the propagating position z can be written as,

,where k and are the wave number and the phase distribution.

Beam CenterFirst moment<x> = 8mm

Propagating slopeSteering Accuracy : -0.3 degree [ in main lobe ]

The complex amplitudes f , g are deduced from the intensity and phase distributions measured and calculated with the fitted wx and Rx in Gaussian Optics. The Gaussian content is evaluated as 0.85 for the output beam.

f , g: Complex amplitude Ae



Transmission Efficiency

To evaluate the efficiency,the intensity patterns are integrated in the x-y plane at the low power test.

A dummy load is connectedat the enterance and the end of the antenna at the high power test. Dummy

load

The efficiency in the imaging property calculation with the higher-order Hermite Gaussian modes [HGm0 modes (m=1-60)] is consistent with those in the measurement.

0.0

0.2

0.4

0.6

0.8

1.0

0 5 10 15 20 25

Low power ExLow power EyHigh power ExCal.[HG00] EyCal.[HGm0] Ey

: m=0-60

Pow

er F

ract

ion

Steering Angle [ degree ]

Tra

nsm

issi

on

Eff

icie

ncy

Trans. eff. : ~0.95

x

yz


The

rmal

dri

ft o

f IF

Am

p.

ECH / ECCD Experiments using Remote Steering Antenna on the TRIAM-1M tokamak

1. Mode Purity Control Experiment----- to optimize and confirm the incident polarization state----

2. O-mode Experiment 3. X-mode Experiment


Halo


Mode Purity Control Experiment in Superposition to LHCD Plasma

The R cutoff radius Rcut is 0.870m. _The plasma center and the bulk resonance radii Raxis and Rres are 0.84m. The maximum resonance radius due to the Doppler shift effect RD is 0.865m.

No coupling area for incident X-mode componentIt is noted that it is ideal to confirm to the O-mode coupling for the incident beam.

R Cutoff


N//~0.22

0.70

0.75

0.80

0.85

0.90

0.95

1.00

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3

Rcut

RD evaluated at R=R

cut

Maj

or R

adiu

s [m

]

N// at R = R

cut

Current Drive(CD) Window for X-mode

Raxis

Rcut RD

low field side ne = 0.8 x 1019 m-3 in the target LHCD plasma

Rcut >RD

0

5

10

15

20

I p [

kA]

+13 degree case

0.00.51.01.52.02.53.0 Isx14(R0.79m)

Isx9(R0.84m)Isx6(R0.88m)Isx5(R0.89m)Isx4(R0.9m)

-0.2 0 0.2 0.4 0.6 0.8 1 1.2

I S

X [

a.u.

]

0.0

0.5

1.0

1.5

0 0.2 0.4 0.6 0.8 1

IHx6(R0.79m)IHx5(R0.81m)IHx4(R0.84m)IHx3(R0.86m)IHx2(R0.89m)IHx1(R0.91m)

I H

X [

a.u.

]

Mode Purity for O-mode

Halo


Mode Purity Control Experiment

The increase of the current comes from a coupling of Electron Cyclotron Wave to the LHCD plasma.


LH 60kW

~30kA

~0.8x1019m-3Raxis

ECH/ECCD 100kW

N//~0.22 Purity 1.0

Purity 1.0

Purity 1.0

Purity 1.0(center)

(center)

Ip

ne

SX

HX

OII

Halo


Steering Angle Scan in the O-mode Experiment

The heating effect in an improvement of the LHCD efficiency is dominant.

The increased current Ip in the perpendicular injection is 18.3 kA.

The current drive efficiency ECHLH= neIpR/(PECHPLH) in the superposition is evaluated as 0.325 x 1019 A/Wm2.That is comparable to LH of 0.378 x 1019 A/Wm2 in the target LHCD plasma.

0.0

5.0

10.0

15.0

20.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

-0.2 -0.1 0.0 0.1 0.2

-15 -10 -5 0 5 10 15

Ip [kA]

Calculated Optical Depth

Ip [

kA]

[n

e:2

x1019

m-3

;Te:

700e

V]

N// at R=Rres

Steering angle [ degree ]



0.0

0.5

1.0

+ 16 degrees [co- injection] - 16 degrees [counter- injection]

0.75 0.8 0.85 0.9 0.95

I SX

[a.

u]

R [m]

0.0

0.5

1.0

1.5 +16 degrees [co- injection] -16 degrees [counter injection]

I H

X [

a.u]

Peaked IHX Profile in the Co- Steering Case at the O-mode Injection

The peaked IHX profile in the co- steering case suggests a direct coupling into the forward fast electrons at between R= RD and R= Rres.

In the co- (+16 degrees) and counter- (-16 degrees) steering cases, the forward (v//>0) and backward (v//<0) fast electrons can be coupled with the incident wave between RD and Rres before the beam is absorbed by the bulk electrons.


20

25

30

35

40

1.4 1.5 1.5 1.6 1.6 1.7 1.7 1.8 1.8

I p [kA

]

ECH ~ 100kW

Counter- injection[ -19 degrees ]

Co-injection [ +19 degrees ]

ECCD

0.2

0.4

0.6

0.8

1.4 1.5 1.6 1.7 1.8HX

Int

ensi

ty a

t C

ente

r C

ode[

arb

. uni

t ]

Co-injection [ +19 degrees ]

Counter- injection[ -19 degrees ]

Time [s]

ECH ~ 100kW

Halo


X-mode Experiment in the Doppler-shifted ECCD in LHCD plasma

The parallel refractive index N// is 0.32 The Doppler resonance RD is 0.868m. The R cutoff position Rcut is 0.860m. There is a Current Drive (CD) window between RD and Rcut, where the X mode can be absorbed.


At same ne=0.95 x 1019 m-3

There are clear differences in the both steering cases in the increased current and the HXR intensity.

0.70

0.75

0.80

0.85

0.90

0.95

1.00

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3

Rcut

RD evaluated at R=R

cut

Maj

or R

adiu

s [m

]

N// at R = R

cut

Current Drive(CD) Window for X-mode

Doppler Up-shifted ECCDfor X-mode

RD

Rres

RcutRaxis

Off-axis

Halo


0.30

0.35

0.40

0.45

0.50

0.75 0.80 0.85 0.90 0.95

I H

X [

a.u

. ]

R [ m ]

plasma center

CD Window

The hollow IHX profile is observed with a peak at the CD window. It indicates the incident X-mode wave is coupled around R=0.86m.


0.0

0.2

0.4

0.6

0.8

1.0

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

p

p//

10 keV

70 keV

Resonanceat R=0.86m p

// = /N

pThe possible energy range to be resonant with the incident X-mode at R=0.86m is evaluated as 10-60keV. The resonant energy range for the EC wave is consistent with that of the forward fast electrons by the LH wave.

ECCD in X-mode Coupling to Fast Electrons in LHCD plasma

Ip is due to the ECCD effect on a coupling for the forward fast electrons in the LHCD plasma.

Summary (I)

The symmetric direction remote steering antenna with larger steering angle has been developed for the ECH/ECCD experiments on the TRIAM-1M tokamak. The steering angles of 8-19 degrees are available, in addition to that near 0 degree.

The output beam from the antenna is the well-defined Gaussian beam with a correct steering angle.

The Gaussian content and the steering angle accuracy are 0.85 and –0.3 degrees.

The transmission efficiency is evaluated as 0.95 in the high power test.

In the O-mode experiments, the dependence of the increased current on the steering angle is observed. However, the heating effect in an improvement of the LHCD efficiency, compared to the ECCD effect, is dominant.


In the X-mode experiment, there are clear differences in Ip and IHX in the larger co- and counter- steering cases due to the ECCD effect on the coupling for the forward fast electrons in the energy range of 10-60keV at the medium density (1x1019m-3). The hollow profile of the HXR intensity increased by ECH/ECCD is observed at the CD window.

The resonant energy range is consistent with that of fast electron generated by the LH wave.

_The CD efficiency is roughly evaluated from the difference of the increased current (~ 5kA) between the co- and counter- steering cases as ten times smaller than that in LHCD.

Summary (II)

This is a first application of the remote steering antenna to the ECH/ECCD experiment.


The energy range of fast electrons coupled with EC wave is equivalent to that of resonant electrons for ECCD in high electron temperature plasmas at ITER.

fundamental x-mode electron cyclotron current drive

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