development status of kstar lhcd system - welcome...

Development Status ofDevelopment Status ofKSTAR LHCD SystemKSTAR LHCD System

September 24, 2004September 24, 2004

Y. S. Y. S. BaeBae, M. H. Cho, W. Namkung, M. H. Cho, W. Namkung

Plasma Sheath LabPlasma Sheath Lab..Department of Physics, Department of Physics, PohangPohang University of Science and TechnologyUniversity of Science and Technology

Development Status of KSTAR ECH and LHCD System (September, 2004) 2

LHCD system overview

Objectives• Required for the the steady-state operation of KSTAR.• Non-inductive current drive • Off-axis current-profile control, so that q profile control, • Efficient bulk current drive at low plasma temperatures, • Electron heating.

RF source: Four TOSHIBA Klystrons (5-GHz, 500 kW CW)Transmission line system:

• Oversized circular waveguides between klystron and divider/phase shifter networks for low RF loss

• 3-dB dividers (standard WR187 waveguide size)• Phase shifters• DC breaks• Etc

Power dividing and phase shifting network


Conceptual schematic of the transmission system

Klystron

3-dB divider

Dummy-load

E-plane taper

Launcher

Phase shifter

3-dB splitter


Power dividing and phase shifting network

Directionalcoupler

DC Break

Oscillator& driver

Low power phase shifter

High powerphase shifter

Medium powerphase shifter E-Taper

DummyLoad

Klystron

3-dBDivider

1

Launcher

Network 1

Network 2

3-db splitter

Network 3

Network 4

Waveguide antenna (Grill)

32 waveguides

4 w

aveg

uide

s

Column 1

Column 2

Column 8 h = 5.5 cm

b = 0.55 cm

t = 0.15 cm

Waveguide dimensions at grillOne klystron feeds RF power to 8 columns of the grill


Power coupling at grill of the LHCD launcher

1E12 1E13

0

10

20

30

40

50

Ref

lect

ion

(%)

Edge density scan (cm-3)

Number of Waveguide : 32, Scale length, Ln = 1 cm ∆φ = 60o ∆φ = 90o ∆φ = 120o ∆φ = 150o

-8 -6 -4 -2 0 2 4 6 8

0

500

1000

-40

-20

0

20

40

60

80

100

A.U

.

N|| (Nz)

∆φ = 60o

∆φ = 90o

∆φ = 120o

∆φ = 150o

Number of Waveguide = 32Edge Density = 1.0 x 1012 cm-3, Ln = 1 cm

Aver

age

pow

er c

oupl

ing

(%)

60 80 100 120 140 1600

102030405060708090

100

xp = 5 mm

xp = 2 mm

xp = 1 mm

xp = 0 mm

Ref

lect

ion

(%)

Phase difference (deg)

Edge density = 1.0 x 1018 m-3, Density gradient = 1.0 x 1020 m-3

Edge density scanWith density gradient of1 x 1020 m-3

xp is the vacuum gapdistance betweengrill and plasma

PIC simulationFor LH-wave propagationin high density plasmaLoaded with density gradient Ed

ge d

ensi

ty: 4

x 1

019

m-3

Den

sity

gra

dien

t: 8

x 10

21m

-3


Design progress of 5.0-GHz LHCD launcher

• Conceptual physics design of the single waveguide channel has been done (using HFSS and ANSYS)– E-plane taper– 3-dB power splitter– Fixed phase shifter– Water-load

• Co-work with PPPL for the KSTAR launcher design– It has many of the design feature of C-MOD launcher (5 sec operation)– However, the near steady-state of KSTAR operation (300 sec) presents

some new challenges which will require new launcher design features• Better heat removal from the coupler grill• Shielding of the microwave windows from direct line of sight to the plasma • Compact water loads for capturing power reflected from the grill/plasma

interface– The collaboration with PPPL is expected to provide a suitable steady-state

launcher design for KSTAR.– A reasonable cooling structure is presented by Dr. J. Hosea in US-KO

collaboration meeting, May 19.


C-MOD Launcher

frontcoupler

vacuum window H-taper

3 dB splitter

E-taper

shortor dump

loadsdiagnostic

probes

diagnosticprobes

C-MOD port flange


Launcher DesignPhased-array waveguide antenna• Waveguide channels

- Waveguide pattern milled on the metal plate (3-dB power splitter, phase shifter, H-plane taper, water-load)

- 32 metal plates in upper and lower part each

• Grill• Motional structure (wheel, rails,

bellows, etc)

The cross-section view of the launcher

E-plane taper 3-dB power splitterGrillPhase shifting region

Bellows H-plane taperCooling channels


Cold model test results of 3-dB power splitter

Power dividing: -3.43 dB at both outputs Phase shift: 90.30

Return loss: -27.4 dBCoupling to port 3: -27.7 dB

E-plane taper

E-plane taper

Design of Fixed Phase ShifterPrevious Design

• Designed for maintaining two vertical outputs in the same phase.p = 8.1 mm

face to Plasmaboundary surface

( ) ( ) )2

()2(22222

21

φπλπ

λπ

λπ

−−+=+ xyxyG

pG'

2λπφ =

Phase difference betweentwo vertical outputs : 0 degree

Input

H-plane taper

Fixed phase shifter

5.5 cm4.75 cm

x y

λ1λ2 λ′GλG900 delay

φ

0.3 cm

φ is the additional phase delay from p = 8.1 mm.


New Design

pyxyx

yxyx

bbaa

bg

bg

ag

ag

++=+

++=+2

2222

2121

πλπ

λπ

λπ

λπ

tyb

xb

p

ya

xat

47.5 mm

47.5 mm 55 mm

55 mm

Primary arm

Secondary arm90o delay

KSTARPlasmaBoundary

• Offset the start position of the tapering between two arms.

mm) 86.74( mm 86.74

mm 11.4 mm, 71.6,mm 77.4

)(4)4(

21

21

21

+=∴−=−

===

−

−=−

abba

gg

gg

ggba

x xxx

p

pxx

λλ

λλλλ


HFSS Simulation

3-dB power splitter, H-plane taper, and fixed phase shifter

Input port

In phase output Out-of phasereflection

Water-load


Steady-state LHCD Launcher Grill Design

In collaboration with PPPL

Top of grill water cooled to within 5 mm of front

Glidcop septum

255 °C

SS insert

314 °C 549 °C

Glidcop/SS Sandwich

KSTAR LHCD Launcher


Placement of Windows

• The windows for the C-MOD LH coupler are placed in the grill nose• The placement of the windows for KSTAR launcher need to be placed after

splitter if possible - but where f (5 GHz) < fce on the vacuum side• This placement will need to be an integral part of the launcher design

Cooled SS vacuum flangeCeramic windowlocation

Titanium guide

Alcator C-MOD window locationKSTAR window location

Ceramic window location

Ceramic window location

7 m

Low vacuum due to bad pumping conduction

fce = 28 BT R0/R = 28 x 3.5 x 1.8/7 = 25.2 GHzf < fce (OK)


Compact Reflected Water-loads of Arm 4 of Splitter

• Minimization of the recirculation of reflected power is essential for controlling the spectra

– Shorting plates are acceptable for equal reflections from the guide ends poloidally

– Compact loads are needed for non-uniform reflections(e.g., for vertical plasma shifts and arcs)

• Water tube insertion designs have been studied– Heat transfer is not totally satisfactory and insulating tubes

may prove too fragile

• Improved design needs to be developed

3-dB power splitter

Placement ofWater-loads


Improved Design of Water-load

L = 2 λG, α = 0.5, s = 19.6 mm, d = 19.8 mm

HFSS simulationVSWR = 1.00038 at 5.0 GHz(Reflection = -37 dB)

ANSYS analysis for temperature distribution

• Maximum temperature : 61 oC• Constraints for water cooling

film coefficient = 4 W/cm2 oKbulk temperature of 300 oK

(VSWR < 1.001 and maximum temperature < 70 oC )


Summary and proposal alternatives for US support

• We propose to help address the important steady-state LH launcher issues– Design, analyze and prototype (at high power) fully active grills that can sustain

steady-state operation on KSTAR - a Glidcop/SS sandwich design is probably best for heat/disruption loads

– Design proper placement of windows out-of-sight of plasma– Develop new compact water load for arm 4 of splitter - design and

prototype (low and high power)

This task is estimated to take two years at ~ $400 k per year

• We could also undertake to design and fabricate the entire LH launcher for KSTAR– This would involve integrating the designs above into a splitter/guide

arrangement that would fit into the KSTAR port envelope– Most likely a three-way splitter poloidally would be designed so that the

number of windows could be reduced to 32 and could all be placed inside theport space

This task is roughly estimated to take ~ 3 years after the development aboveand to cost ~ $5 M in as spent dollars with 30% contingency.


Proposed schedule and cost by PPPL

KSTAR 1.5 MW LHCD Launcher Schedule

2005 2006 2007 2008 2009 2010

Design/develop concept for steady-state grill, power splitter, launcher,window placement, water load

Projected Costs with Inflation and 30% Contingency

400 k 400k 1.0 M 2.0 M 2.0 M

Prototype steady-state grill, power splitter, water load

Design KSTAR launcher based on prototype results

Fabricate and assemble launcher

• We project that a robust steady-state launcher can be provided for KSTAR at a cost of ~ $ 5 M and can be ready to support operations in 2010

• Two years of R&D prior to design of the launcher is needed to assure theviability of the launcher and its potential relevance to ITER


5 GHz RF test System

RF test system ofa single waveguide ofLHCD launcher

PFN Pulse Modulator(Max 45 kV, 96 A, 4 µs)

5 GHz, 1.5 MW,1 µs, magnetron

Pulse TR

Cathode Voltage

Cathode Current

RF Pulse


5 GHz,1.5 MW CW LHCD System

TOSHIBAKlystron

Power Supplies

5 GHz, 500 kW CWKlystrons

LauncherPPPL, USA

KSTAR

Korea

Waveguide NetworkKorea

EU

DummyLoad

KSTAR ECCD SYSTEM WILL BE DEVELOPED IN COLLABORATION WITH US AND EU.

development status of kstar lhcd system - welcome...

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