lhcd steady-state technology for kstar j. hosea, s. bernabei, r. ellis and j.r. wilson presented at...
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LHCD Steady-State Technology for KSTAR
J. Hosea, S. Bernabei, R. Ellis and J.R. Wilson
Presented at the KSTAR Workshop
General Atomics, San Diego, CA
May 19 - 20, 2004
May 2004
LHCD Steady-State Technology for KSTAR
• The present LHCD design for KSTAR has been developed based on TPX considerations and with PPPL supporting the KSTAR team effort
• It has many of the design features for the C-MOD LHCD system– C-MOD operation will serve to test these features for relatively short pulses (5 sec)
• However, the near steady-state of KSTAR operation (300 sec) presents some new challenges which will require new coupler 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
• We propose to enhance our collaboration with KSTAR to help address these challenges and provide a suitable steady-state launcher design for KSTAR
May 2004
Very Good Spectral Control isProvided by Phasing of Each of32 Columns of KSTAR Design
• Maintaining this spectral control will be a primary objective for the steady-state KSTAR design
• 32 columns x 4 rows = 128 active guides
• 4 x 0.5 MW klystrons power 8 columns each
• Each column is individually phase controlled with high power phase shifters
• Microwave windows need to be placed outside of stacked coupler region to avoid sight of plasma
May 2004
The power splitter/grill guides and water loads fit into a very compact design
• It is important to maintain this compact design to preserve spectral control and to minimize waveguide losses• Cooling of the components - grill, guides, and loads - is more difficult for a compact design
Input
Input
H-plane taper
Fixed phase shifter
4.75 cm 5.5 cm
Capacitivebutton
Plasma boundary
Matched load
May 2004
Design of coupler assures that wavefronts are in phase at the mouth of the coupler
• The capacitive button, and fixed phase shifter provide for good power splitting vertically with very little power going to the load guide
– P2/P1 = - 3.04 dB – P4/P1 = - 3.07 dB– P3/P1 = - 43.07 dB
Pin 1
Pload 3
2 Pout 2
4 Pout 4
May 2004
C-MOD LHCD Antenna has a Similar Design to KSTARKLYSTRONlow power
phase shifter24193 dB splitter10#5high power
phase shifter
• 24 columns x 4 rows = 96 active guides
• 12 x 0.25 MW klystrons power 2 columns each
• Each column is individually phase controlled with high power phase shifters
• Microwave windows are placed in nose of coupler
May 2004
C-MOD LH Launcher System - Elevation View
frontcoupler
vacuum window H-taper
3 dB splitter
E-taper
shortor dump
loadsdiagnostic
probes
diagnosticprobes
C-MOD port flange
May 2004
02468100510152025 power flux in the waveguidesf2b (GHz2 cm)kW/cm2breakdownweak conditioning
waveguide dimensions 6.0x0.55 cm2*Æ2.3 MW net power (12 Klystrons - 24 kW/guide)1.5 MW net power (8 Klystrons - 15.5 kW/guide)*ÆJET 2 secJET, TS long pulse PBX-M 0.5 sec££ûû
C-MOD
KSTAR
f2b (GHz2 cm) • C-MOD LH operations will serve to test short pulse (5 sec) features of the
KSTAR design• Critical steady state (300 sec) design features required for KSTAR LH design
1..5 MW net power (4 Klystrons - 11.7 kW/guide)
Waveguide dimensions:KSTAR - 5.5x0.55 cm2
C-MOD - 6.0x0.55 cm2
Power Flux in the Waveguides for KSTAR and C-MOD
kW/cm2
May 2004
Heat Removal From the Coupler Nose is the Major Critical Issue for Steady-State
• Two possible solutions for KSTAR LH coupler cooling:– Incorporate Frascati ITER PAM (passive-active- multi-junction) grill cooling design
good cooling but reduces active guides by half and reduces directivity of spectrum
– Design cooling into the present stacked plate KSTAR coupler design Heat conductivity of 2 mm SS septum is two low Material must be changed to Glidcop or CuCrZr or cooling tubes imbedded into septum
• We propose to keep optimum spectral control - design cooling into the stacked plate design
– LHCD operation on KSTAR can then serve to set the optimum phase properties for the ITER PAM design and possibly lead to a better launcher option
May 2004
Frascati PAM LH Coupler
• Cooling of passive guides between all active guides
Active guide
Passive guide
F. Mirizzi et al., Fus. Eng. Des. 66-68 (2003) 621.
May 2004
EU ITER LH PAM Design for Water Cooling
SS cooling pipes HIP imbedded into beriliumpassive guide spacer plates
Glidcop or CuCrZr used foractive guide wall plates
P. Bibet and F. Mirizzi, CEA:EFDA/00-553; ENEA;EFDA/00-554 (2001)
May 2004
Top/Bottom Cooling of Stainless Steel Fully Active Grill is not Acceptable
Top of grill water cooled to within 1 cm of front
100 W/cm2
from plasma
1181° C
• Temperature at center of septum reaches 1181° C in steady state
SS
May 2004
Inserting Dummy (Passive) Guides Between Active SS Guides Gives Better/But Not Sufficient Cooling
• 1170° C still too high for steady-state• Making septa out of Glidcop does give a reasonable temperature of 410°C• However, a solution without passive guides is preferred for spectral flexibility
Cooled top
Glidcop septum
Cooled top
Midplane
1170°C 660°C
Midplane
SS septum
320°C 410°C
May 2004
Top/Bottom Cooling of Fully Active Grill With Glidcop SeptaGives Sufficient Cooling for Steady-State
• This is the preferred design for KSTAR to assure optimum spectral selection and directivity
Top of grill water cooled to within 5 mm of front
Glidcop septum
255° C
SS insert314° C
549° C
May 2004
First Pass Power Spectrum for Fully Active vs Passive/Active Grill
0 1 2 3 4 5
0
1 0 0 0
2 0 0 0
3 0 0 0
4 0 0 0
5 0 0 0
6 0 0 0
n parallel
Pow
er
a.
u.
all waveguides active
every other waveguide is passive and 90 phasedo
same total power
directivity
60 o
90 o
120 o
60o
90 o
120 o
with 90o passive
with 90o passive
with 90o passive
95%
90%
80%
79%
58%
50%
Passive/Active
Fully Active
60°
90°
120°
120°
90°
60°
• Fully active grill gives much better directivity and a wider range for n ||
• If lower n|| proves to be optimum on KSTAR then the PAM design may prove to be acceptable for ITER
May 2004
Placement of Windows Out of View of Plasma is Desirable for Steady-State
QuickTime™ and aPhoto - JPEG decompressor
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Stacked guide/power splitter
Source 1 feed
Phase Shifter
Dummy load
3 dB hybrids
Cooled SS vacuum flange
Ceramic window location
Titanium guide
C-MOD window location Feed guide/power splitter system for C-MOD
• 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 < fce on the vacuum side• This placement will need to be an integral part of the launcher design
May 2004
Further Development of Compact Reflected Power Loads for Arm 4 of Splitter is Proposed
water inwater out
• 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
May 2004
Summary and Proposal Alternatives for US Support of LHCD on KSTAR
• 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 the port space
This task is roughly estimated to take ~ 3 years after the development above and to cost ~ $5 M in as spent dollars with 30% contingency.
May 2004
Proposed Schedule and Cost for the KSTAR LHCD Steady-State Launcher
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
Prototype steady-state grill, power splitter, water load
Design KSTAR launcher based on prototype results
Fabricate and assemble launcher
Projected Costs with Inflation and 30% Contingency
400 k 400k 1.0 M 2.0 M 2.0 M
• 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 the viability of the launcher and its potential relevance to ITER