Shin KUBO, Masaki NISHIURA, Kenji TANAKA, Takashi SHIMOZUMA, Yasuo YOSHIMURA, Hiroe IGAMI,

Hiromi TAKAHASHI, Takashi MUTOHNational Institute for Fusion Science

Collective Thomson Scattering Study using Gyrotron in LHD

Research Center for Development of FIR Region, Univ. of FukuiYoshinori TATEMATSU, Teruo SAITO

Namiko TAMURA,Dept. Energy Science & Technology, Nagoya Univ.

US-Japan Workshop on RF Physics2010.03.8-10 General Atomics, San Diego　

Contents

•ECRH System in LHD --> Potential as a diagnostic tool•Collective Thomson Scattering•Receiver•Preliminary results•Scattering Volume and CTS spectrum•Sub-Tera Hz Gyrotron Development•Future Plan•Summary

ECRH System

Design of the Antenna System of ECRH in LHD

• Two sets of upper antennas from 5.5U and 9.5 U port for 82.7GHz and 168GHz

• Two 84 GHz Antenna from 1.5 L port

• All antennas can focus and deposit the power within r<0.2 for Rax=3.53m,B=2.951 T

• Antenna Scan Range– U antenna

• R=-3.2-3.8m, t=±0.2m on mid plane

– L antenna• R=-3.0-4.2m,t= ±1.5m

6

Elliptical Gaussian Beam Focusing Scheme

168GHz Beam

SteeringMirror

FocusingMirror

from Waveguides

84GHz Beam

SteeringMirror

FocusingMirror

mid-plane Focusing MirrorBi-focal Mirror

Waveguide mouth

Hot test of beam steering/focusing• Errors of steering for tor/rad-directions notably affect deposition profile• Beam steering/focusing were checked in vacuum vessel of LHD by using

Kapton film and IR-camera.

ECRH Beam as a Scattering Probe Beam• Well defined beam for heating is also suitable

for probe beam for scattering measurement.– High power density, High Frequency

Modulation• Good S/N Ratio

– Controllable• Scattering Cross Section Position• Scattering Angle

• Promising Candidate for– Density Fluctuation Measurement

• Structure study of micro-turbulence– Wave detection

• EC wave, LH wave, IC wave, Alfven wave– Collective Thomson Scattering

• Ion temperature measurement• Alpha particle distribution study

EC wave, LH wave, IC wave, Alfven wave

9

Collective Scattering using

ECRH System

10

Collective Scattering Condition

3

θ =10 deg θ =90 deg

11

LHD ECH Antenna Configuration (2008)

9.5U Antennaout 82.7 GHzin 77 GHz

5.5U Antennaout 82.7 GHzin 168 GHz

1.5L Antennaout 84 GHzin 84 GHz

2-O Antennaright 77 GHzleft 168 GHz

3.5 inch corrugated WG

3.5 inch corrugated WG

3.5 inchcorrugated WG

1.25 inch corrugatedWG

12

LHD ECH Antenna used for probe and receiving beams

3

9.5U Antennaout 82.7 GHzin 77 GHz

5.5U Antennaout 82.7 GHzin 168 GHz

1.5L Antennaout 84 GHzin 84 GHz

2-O Antennaright 77 GHzleft 168 GHz

3.5 inch corrugated WG

3.5 inch corrugated WG

3.5 inchcorrugated WG

1.25 inch corrugatedWG

waist size 0.015 mwaist size 0.02 m 0.8 MW/5s, 0.24 MW/CW

13

Present ECRH System in LHD

•Two sets of transmission line/ antenna are installed on the ports. •9.5U, 5.5U 1.5L and 2O

14

Proposed Scattering Probe/Receiving transmission Line

•A set of transmission line/ antenna on the 9.5U port is used for CTS.•A line which 77GHz 1MW power available is used for probe beam

15

Receiver Setting Configuration

16

Attached Receiver System

plasma

f0+df

f0+df+fs

gyrotrondf~200MHz

power monitor

ECRH Transmission line(corrugated waveguide)

fixed local oscillatorstability < 10 MHz

pin SW

Notchfilter

Att. BPF

WG SW

Filtek HPF

fl=78 GHz

Mixer

A1

A2A3

Isolator

Two way divider 1

Two way divider 2

high freq.

low freq.

500-200

900-200

1300-200

1700-200

1900-100

2100-100

2300-100

2500-100

Four way divider Diodes

Video Amps.(x1000)

monitor port

measure port

A1: Cernex CBLU1103030-01A2: Cernex CBLU1103050-01A3: Amplitek apt4_SN104331

Heterodyne Receiver for Collective Thomson Scattering in LHD (2008)

Filter CombinationLocal Oscillator 74 GHz

•Filter combination•Center freq.

•IF 3 GHz•sensitive low freq. IF

•for high energy ions•narrow band dense near center freq. IF

•for bulk ion•wide band sparse at peripheral IF

•for high energy ions

Actual Receiver Configuration

IF Amps.

WaveguideSwitch

Splitters

Filters

Mixer

Local Oscillator

PIN Switch

Notch Filter

Horn Antenna

Waveguidefor Probe

Beam

From 77 GHz Gyrotron

During the first trial of CTS measurement,the local oscillator of 74 GHzwas damaged,

Actual Filter Combination

and switched tentatively to78 GHz Courtesy of Dr. T. Tokuzawa

Ch.1,4,5 double side bandCh.2,3,6-8 lower side band

Background, calib.

CTS componentAll channel lower side band Ch2,3 almost notched

10-3

10-2

10-1

100

0 1 2 3 4 5 6 7 8 9

%) /# &)*312!( $,( "'.0-/, '.+, &)*312 !( $,( "

Cal.

Fact

or(V

/eV)

Channel

2009.01.23ΔT=210 deg. lock-in factor=3.0

Effect of Notch Filter

Actual Filter Combination and Calibration with Liq N2

78GHz local combination

Measured Notch FilterCharacteristics Courtesy of Prof. A. Mase

FilterCharacteristics Courtesy of Prof. Y. NagayamaDr. T. YoshinagaMr. D. Kuwabara

Actual Measurement Configuration

B=2.75 TR=3.6 mrho=0.7±0.2k ~ perpendicular

25

Preliminary Results

✴B=2.75T, R=3.6m✴Fundamental ECRH Plasma

Fundamental ECRH plasma ✴B=2.75T, R=3.6m✴Fundamental ECRH Plasma• Noise well suppressed•Spikes at every modulation turn-on, off

•due to spurious mode oscillation from gyrotron•removable by pin switch

Fundamental ECRH plasma (double side band factor)

Expanded in time (#91758)

Expanded in time (#91758)

CTS #91758 (double side band factor)

✴B=2.75T, R=3.6m✴Fundamental ECRH Plasma• Noise well suppressed•Spikes at every modulation turn-on, off

•due to spurious mode oscillation from gyrotron•removable by pin switch

CTS #91758 (double side band factor)

✴B=2.75T, R=3.6m✴Fundamental ECRH Plasma• Noise well suppressed•Spikes at every modulation turn-on, off

•due to spurious mode oscillation from gyrotron•removable by pin switch

Analysis ECRH plasma

Decompositionof scattering

component from heating/heat

wave componentis necessary

Method of analysis• Raw data of several modulation periods are

rearranged in time relative to the turn on/off time

• These rearranged data are fitted with the function

• δa corresponds to background increments/decrements due to heating (change in slope)

• δb corresponds to increment/decrement due to scattered signal over background (stepwise change)

Example of deduced raw signal change

Spectrum change in time

Example of deduced scattered power spectrum

36

Receiver Improvements

Heterodyne Receiver for Collective Thomson Scattering in LHD (2009)

fixed local oscillatorstability < 10 MHz

pin SW

Notchfilter

Att.

BPF

WG SW

fl=74 GHz

MixerIsolator

HPF

A1 A2

A3

A4A4

A4A4

A4A4

A4A4

A3

n

ECRH Transmission line(corrugated waveguide)

5th-HarmonicMixer

n

fl1-ndf

A5

HPF

Att A5

HPF *

HarmonicMixer

Error AmpVoltage Controlled

Oscillator

plasma

f0+df

f0+df+fs

gyrotrondf~200MHz

power monitor

ADC

ADC

ADC

ADC

32 channel VideoAmp.(x100)

LPF

Filters

Low NFAmps

PowerAmps

2<f<8GHz

f<6GHz

f>0.3GHz

0.5<f<4GHz

0.5<f<18GHz

Increased IF bands local frequency = 74.00 GHz

IF filter characteristics

40

Scattering Volume• Key to confirm scattering signal

confirmation• Necessary for absolute calibration

Beam Cross Section Controlled by beam steering

receiving beamprobing beamprobing beam receiving beam

ρ=1.0

ρ=0.19.5U in 77GHz injection9.5U out receiving

Max cross section at ρ=0.75 Zero cross section

• Scattering power

is obtained using scattering form factor

Γ: geometrical factorre: classical electron radiusne: electron densitydω: band widthrR: beam radiusλs0: wavelength of scattered

radiationS(k,ω): scattering form factor

Probebeam

Scatteredbeam

fromGyrotron

toReceiver

SN ratio of CTS

43

Scattered Power

U-antenna for 168 GHz used for 77 GHz Scattering

•Beam evolution is recalculated with the 168 GHz antenna mirror configuration radiated from the same waveguide mouth for 77 GHz beam •Resultant beam sizes on the mid-plane are •20 mm in radial •99 mm in toroidal

If the configuration of the mirrors and optical axis are the same,i. e. cosφ and ρ are kept ,relation between Rin and Rout are defined by

even for different frequency, or beam size

77 GHz168 GHz

bi-focal mirrorfinal focus mirror

7777

45

Scattering using Gaussian Beam

46

Cross Volume of Gaussian Beam

47

Surface of Cross Volume

48

Cross Volume and resolution

49

Scattering using Gaussian Beam

Scattering Length

50

Scattered intensity and effective scattering length well scale

center

top

bottom

Scattered spectrum are fitted with offset-Gaussian to subtract ECE background

Intensity ratio of the scattered power well scales to the calculated effective scattering length

Comparison of Exp. / Cal. Spectrum

51

Measured data are used for calculation.• Te=0.6keV• TAr=0.7keV• ne=2.5x1019m-3

• nfast=0.1x1019m-3

• Ti=0.7keV is better fitting than Ti=2keV.

• Measured data seems to have an offset of +0.1GHz.

• P(3.6,0,0), R(3.6,0,0)• Vsc=153.3cm3

1

10

100

1000

-3 -2 -1 0 1 2 3

Calculated CTS spectrumscattered radiation

Scat

tere

d Po

wer

(eV)

frequency (GHz)

52

Sub-Tera Hz Gyrotron

Development

FIR FUCTS in LHD

fi > 4fce suppression of ECE400 GHz band is one choice. Salpeter Parameter

Linked with slide 15

R along scattered wave path (m)

FIR FU

Achieved 50 kW

• More than 50 kW at 349 GHz and about 40 kW at 390 GHz have been achieved. These are highest powers as second harmonic oscillation of gyrotron.

• Oscillation efficiency decreases for large beam current possibly due to degradation of the quality of the electron beam.

From Notake PRL paper

Vk = 57 kV

Future Plan• Establish Calibration/Analysis procedure

• Scattering Volume

• CTS spectrum and reduction of ion/fast ion temperature

• Calibration including polarizer/waveguide coupling

• Multi receiver / fast volume scan• Precise background subtraction

• Simultaneous measurement in 2-D velocity space

• Expansion in real/velocity space

• Sub-Tera Hz Gyrotron Application to CTS

57

LHD ECH Antenna used for probe and receiving beams

3

9.5U Antennaout 82.7 GHzin 77 GHz

5.5U Antennaout 77 GHzin 168 GHz

1.5L Antennaout 84 GHzin 84 GHz

2-O Antennaright 77 GHzleft 168 GHz

3.5 inch corrugated WG

3.5 inch corrugated WG

3.5 inchcorrugated WG

1.25 inch corrugatedWG

waist size 0.03 m 0.8 MW/5s, 0.24 MW/CW

ECRH Horizontal Antennafor parallel component

• 2 sets of• Focusing Mirror

• Symmetric Gaussian Beam

• 35 mm waist size at plasma center

• Steering Plane Mirror• Toroidally +/- 30

degree• Poloidally +/- 10

degree

Summary•Started CTS utilizing ECRH system in LHD77GHz ( P~1MW) Gaussian beam is used as a probe.Injection ECRH antenna is used as a receiver. Backward, perpendicular 8/32 channel receiver system is attached to ECRH transmission line 3 s, 50 Hz modulated injection at 0.7 MWPreliminary results with 8/32 channel show promising CTS signals

•32 channel•Higher reliability in ion velocity distribution reduction

•Examining possible use of horizontal antennas•Backward, parallel components

•Sub-THz gyrotron developed for CTS in LHD