Plasma Visualization Diagnostics for KSTAR: ECEI and MIR

C.W. Domier, N.C. Luhmann, Jr.University of California at Davis

FY09 US-KSTAR Collaboration WorkshopApril 15-16, 2009 – San Diego, CA

UC DAVISPLASMADIAGNOSTICSGROUP

Outline

● Introduction and Overview

● Diagnostic Principles– Te Measurements via ECEI

– ne Measurements via MIR and MDIR

● Experience on Previous and Current Systems

● Ongoing Development Activities

● Low Field (~2 T) and High Field (3-3.5 T) Conceptual Designs

● Diagnostic Development Plan

Outline

● Introduction and Overview

● Diagnostic Principles– Te Measurements via ECEI

– ne Measurements via MIR and MDIR

● Experience on Previous and Current Systems

● Ongoing Development Activities

● Low Field (~2 T) and High Field (3-3.5 T) Conceptual Designs

● Diagnostic Development Plan

Introduction and Motivation●A unique window of opportunity exists

on KSTAR for fundamental understanding of MHD and turbulence not possible with ITER and future burning plasma experiments

–Excellent port access

–Advances in 3-D simulation capability

–Advances in imaging diagnostics capability

●2-D plasma microwave imaging tools–Electron Cyclotron Emission Imaging

(ECEI)

–Microwave Imaging Reflectometry(MIR)

–Microwave Doppler Imaging Reflectometry (MDIR)

Outline

● Introduction and Overview

● Diagnostic Principles– Te Measurements via ECEI

– ne Measurements via MIR and MDIR

● Experience on Previous and Current Systems

● Ongoing Development Activities

● Low Field (~2 T) and High Field (3-3.5 T) Conceptual Designs

● Diagnostic Development Plan

2-D ECE Imaging (ECEI)● In conventional 1-D ECE

radiometry, a single antenna receives all frequencies. In ECEI, a vertically aligned antenna/ mixer array is employed as the receiver.

● Advantages: high spatialand temporal resolution,2-D correlation.

● Real time 2-D imaging using wideband IF electronics and single sideband detection.

– 16×8=128 channels on ASDEX-UG

– 20×16=320 channels onDIII-D

– 24×32=768 channels envisaged for KSTAR

fce

R

fce

R

VideoAmps

Mixers

IF Amps DetectorsAntennas

Mixers

Baluns

Preamps FiltersPower Divider

LO

LOnNotch Filter

ADCs

PlasmaOptics

ECEI System Overview – TEXTOR

Dichroic Plate

LO1

Imaging Fluctuation Reflectometry

● Microwave reflections from plasma cutoffs contain information on density fluctuations near the cutoff layer

● 1-D fluctuations: simple mirror-like interpretation

● 2-D fluctuations: the received signal is corrupted by interference from multiple reflected waves

● Imaging can restore phase fronts!1-D fluctuations

2-D fluctuations

Microwave Imaging Reflectometry (MIR)

● Probing beam illuminates extended region of cutoff layer

● Beam curvature matched (toroidal and poloidal) to that of the cutoff surface

● Cutoff layer imaged onto array of detectors (3 elements shown), eliminating interference effects

● Detection system shares the same plasma-facing optics

Video Amps

IF Amp I-Q Mixer

Antenna

Mixer

Filters

LO

DACs

PlasmaOptics

Beam Splitter

Toriodal Mirror

Window

MIR ArrayLOSource

Illumination Source

Plasma

Poloidal Mirror

MIR Electronics

MIR System Overview - TEXTOR

Microwave Doppler Imaging Reflectometry● Off-axis probing beam is

scattered by Doppler rotation of fluctuations near the cutoff layer

● Optics angularly resolve the reflected/scattered waves onto imaging array

Ray tracing of Doppler reflectometry system on Tore-Supra

Comparison Between MIR and MDIR

● Common features

– Planar imaging array

– Large aperture optics

– Multiple frequencies to probe multiple cutoff layers

● Major differences

– MDIR illumination beamis narrower, and tilted with respect to plasma midplane

– MDIR probes poloidal scattering angle rather than vertical position

MIR

MDIR

Outline

● Introduction and Overview

● Diagnostic Principles– Te Measurements via ECEI

– ne Measurements via MIR and MDIR

● Experience on Previous and Current Systems

● Ongoing Development Activities

● Low Field (~2 T) and High Field (3-3.5 T) Conceptual Designs

● Diagnostic Development Plan

Single Array ECEI on TEXTOR

Single array implementation with 16×8 Te image resolution

TEXTOR Study of “Sawtooth Oscillation”

ECEI demonstrated “random 3-D reconnection zone,” in which the reconnection zone has been observed to occur everywhere (including high field side, see video left)

Single Array ECEI on ASDEX-UG

TEXTOR system transferred to ASDEX-UG in Jan. 2009, and will begin operation in May 2009

Dual Array ECEI on DIII-D

● Horizontal and vertical zoom control with full remote capability

● Two array system, each 20×8 channels expandable to 20×24

● Installation in Sept. 2009, with first results in Oct. 2009

27 cm

1.3 m

Narrow zoom Narrow spacing

Dual Array ECEI on DIII-D

● Horizontal and vertical zoom control with full remote capability

● Two array system, each 20×8 channels expandable to 20×24

● Installation in Sept. 2009, with first results in Oct. 2009

Wide zoom Wide spacing

55 cm

1.3 m

Dual Array ECEI on DIII-D

● Horizontal and vertical zoom control with full remote capability

● Two array system, each 20×8 channels expandable to 20×24

● Installation in Sept. 2009, with first results in Oct. 2009

Wide zoom Wide spacing

55 cm

1.3 m

Outline

● Introduction and Overview

● Diagnostic Principles– Te Measurements via ECEI

– ne Measurements via MIR and MDIR

● Experience on Previous and Current Systems

● Ongoing Development Activities

● Low Field (~2 T) and High Field (3-3.5 T) Conceptual Designs

● Diagnostic Development Plan

Ongoing Development Activities

●Mini-lens imaging array concept and vertical zoom optics

●Horizontal zoom ECEI electronics and frequency extenders

●Quasi-optical notch filters

●High frequency imaging antennas

●Multi-frequency MIR sources

Mini-Lens Array Configuration

Advantages

● Elliptical substrate lens optimizes coupling and reduces sidelobes

● Eliminates off-axis aberrations

● Uses front side LO pumping for enhanced coupling, increased sensitivity and wide bandwidth (octave) operation

LO Beam

Mini-Lenses

Antennas

Beam Splitter

ECEI Array

LO Source

Zoom Control Lenses

Focal Plane Translation Lens

Beamsplitter

New Mini-Lens ECEI System OpticsNotch Filters (3)

New Vertical Zoom Optics

Wide ZoomShot 107808

Narrow ZoomShot 107809

Te images courtesy of Prof. T. Munsat at the University of Colorado

Horizontal spacing and spot size can now be independently and remotely-controlled

New Horizontal Zoom Electronics

7.9 GHz

8.8 GHz

2.5 GHz

3.4 GHz

4.3 GHz

5.2 GHz

6.1 GHz

7.0 GHz

LP Filter

DigitalAttenuator

HP Filter

Power Divider

7.0 GHz

7.6 GHz

3.4 GHz

4.0 GHz

4.6 GHz

5.2 GHz

5.8 GHz

6.4 GHz

Mixer VCO VCO

Multiple Modules for Increased Coverage

Standardized modules can be ganged together to extend RF coverage

– Two modules provide16 GHz coverage

– Three modules provide24.5 GHz coverage

New “Stackable” Notch Filters● Highly collimated mini-lens beams permit

significantly improved ECRH shielding– Relaxed angular requirements (≤ 8°)– Stack up to 3 notch filters in series

● 140 GHz filter stack installed on TEXTOR (single filter results shown below)

● 170 GHz filter stack under development for KSTAR

-35

-30

-25

-20

-15

-10

-5

0

110 115 120 125 130 135 140 145

5 Degree Tilt8 Degree Tilt

Tra

ns

mis

sio

n (

dB

)

Frequency (GHz)

Quasi-Optical Notch Filters

Quasi-Optical Notch Filters

Antennas/Mixers for High-Field ECEI

● Two approaches under investigation to realize imaging antennas for ECEI on KSTAR under high-field (3-3.5 T) conditions

● Fundamental mixers require high frequency (150-220 GHz) sources with >40 mW output power difficult to obtain!

● 2nd harmonic mixers have 2-3 dB worse conversion losses, but can use lower frequency (75-110 GHz) sources readily available!

fRF

FundamentalMixer

fLO

fIF = fRF - fLO fRF

2nd HarmonicMixer

fLO ≈ ½ fRF

fIF = fRF - 2fLO

POSTECH Collaboration (Prof. Hyeon Park) on MIR Characterization

TEXTOR MIR system now set up at POSTECH for detailed laboratory measurements and characterization

PPPL Collaboration (Dr. Gerrit Kramer) on MIR Modelling

2-D simulations of microwaves reflected from a circular plasma, with an illumination beam curvature-matched to the plasma

Kyungpook National University Collaboration (Prof. Kangwook Kim) on

MIR Illumination Sources

Schematic illustrating how a simultaneous “comb” of illumination frequencies can probe multiple cutoff layers, as each frequency reflects from a distinct cutoff layer

Kyungpook National University Collaboration (Prof. Kangwook Kim) on

MIR Illumination Sources

Outline

● Introduction and Overview

● Diagnostic Principles– Te Measurements via ECEI

– ne Measurements via MIR and MDIR

● Experience on Previous and Current Systems

● Ongoing Development Activities

● Low Field (~2 T) and High Field (3-3.5 T) Conceptual Designs

● Diagnostic Development Plan

KSTAR Diagnostic Layout

ECEI Configuration: ~2T

● Low field (~2 T) design for ECEI only

● High field side (HFS) and low field side (LFS) systems share the same zoom optics (inside cassette)

● Two array configuration per port, each generating 24(v)×8(h) Te images expandable to 24×24 images

Plasma

Focal lenses

Vacuumwindow

Zoom lenses

Beam splitter

ToroidallensesCassette

LFS array

HFS arrayMirror

ECEI on KSTAR at 2.0 T

33 cm

100 cm

40

60

80

100

120

140

160

-1 -0.5 0 0.5 1

Fre

que

ncy

(GH

z)

Normalized Radius r/a

3fC

2fC

fC f

R

ECEI

fECRH

High Field Side

Low Field Side

ECEI on KSTAR at 2.0 T

33 cm

100 cm

40

60

80

100

120

140

160

-1 -0.5 0 0.5 1

Fre

que

ncy

(GH

z)

Normalized Radius r/a

3fC

2fC

fC f

R

ECEI

fECRH

High Field Side

Low Field Side

ECEI on KSTAR at 2.0 T

51 cm

100 cm

40

60

80

100

120

140

160

-1 -0.5 0 0.5 1

Fre

que

ncy

(GH

z)

Normalized Radius r/a

3fC

2fC

fC f

R

ECEI

fECRH

High Field Side

Low Field Side

ECEI/MIR Configuration: 3-3.5 T

Plasma

Focal lenses

Vacuumwindow

Zoom lenses

Dichroic Plate

ToroidallensesCassette

ECEI array

MIR array

Beamsplitter

MIR Source

● High field design for simultaneous ECEI and MIR/MDIR

● Two array ECEI configuration, each generating 24×8 Te images expandable to 24×24 images

● Single array MIR/MDIR configuration with a 16 element array and up to 8 simultaneous frequencies/cutoff layers

● Decision to implement MIR or MDIR (or both) dependent upon results from joint POSTECH and PPPL study into MIR physics

ECEI at High Field (3-3.5 T)

High Field Side

Low Field Side

51 cm

100 cm

80

100

120

140

160

180

200

220

240

-1 -0.5 0 0.5 1

Fre

que

ncy

(GH

z)

Normalized Radius r/a

3fC2f

C

fC

fR

ECEI

fECRH

MIR/MDIR

fECRH

MIR/MDIR at High Field (3-3.5 T)

20 cm

100 cm

80

100

120

140

160

180

200

220

240

-1 -0.5 0 0.5 1

Fre

que

ncy

(GH

z)

Normalized Radius r/a

3fC2f

C

fC

fR

ECEI

fECRH

MIR/MDIR

fECRH

Outline

● Introduction and Overview

● Diagnostic Principles– Te Measurements via ECEI

– ne Measurements via MIR and MDIR

● Experience on Previous and Current Systems

● Ongoing Development Activities

● Low Field (~2 T) and High Field (3-3.5 T) Conceptual Designs

● Diagnostic Development Plan

Diagnostic Development Plan

FY2009– Design multi-array low field (~2 T) ECEI system

– Develop multi-frequency source technology for MIR/MDIR (collaboration with Kyungpook National University)

– Fabricate and test high performance 170 GHz notch filters

FY2010– Fabricate and characterize multi-array low-field ECEI system

– Install multi-array low-field ECEI system on KSTAR

– Fabricate and test prototype high-field (3.0-3.5 T) ECEI antennas

– POSTECH and PPPL to complete MIR system tests; results to be used to design optimum MIR and/or MDIR optical configuration

FY2011– Operate and maintain low-field ECEI system on KSTAR

– Design high field (3-3.5 T) simultaneous ECEI and MIR/MDIR system

Thank you for your attention