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KSTAR ICRF transmission line system upgrade for load resilient operation
H. J. Kim, S. J. Wang, Y. S. Bae, H. L. Yang, J.-G. Kwak, S. H. Kima and M. Parka
KSTAR Research Center, NFRIa Fusion Plasma Ion Heating Research Center, KAERI
Japan-Korea Workshop on Physics and Technology of
Heating and Current Drive
Haeundae, Busan, Korea Jan. 28-30, 2013
Outline
q Motivation
q KSTAR ICRF transmission line system upgrade in 2012
q Stable ICRF operation with load resilient T/L system
q Conclusion
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 2
Motivation
q Reliable high power ICRF operation in 2012 KSTAR Campaign
– Fusion plasma is not quiescent and exhibits many transient phenomena such as mode transitions or edge localized modes (ELMs) bursts.
– Plasma density changes and the characteristic of wave propagation is affected.– Plasma density changes and the characteristic of wave propagation is affected.
– An effective load resilient operation is mandatory for reliable ICRF operation.
– In 2011 campaign, we found unstable transmitter power by high reflection.
– Transmitter unstable power at 30.45 MHzà frequency: 30.8 MHz (2012 campaign)
– Tuning problem; inter-strap coupling effect is large.
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 3
2011 campaign
KSTAR ICRF transmission line system upgrade2011 Campaign
2012 CampaignDe-coupler Hybrid splitter
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 4
transmitter
Dummy load
transmitter
Load resilient ICRF T/L system upgrade2011 ICRF system 2012 ICRF system
Dummyload
90 deg. difference
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 5
w/ decoupler
w/o decoupler
90 deg. difference
q Operation of a decoupler
Installation and measurement of a decoupler*
YL
Loop 12
M X dcLoop 34Y
1
2
q Installation and RF test of a decoupler
– Decoupler cancels reactive mutual admittance by adjusting Xdc.
– power balance by allowing coupled power flow through decoupler branch.
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013
– *S. J. Wang et al., Fusion Engineering and Design (In press in FED, 2013)
6
30.8 MHz
High power operation with a decoupler
q Operation of a decoupler at 180 deg. between loop A and B (2011 vs. 2012)
– Power ratio (PA/PB): ~ 1 (2012)à Decoupler works very well.
– 400 kW, 3 s stable operation: FWD ~ 400 kW, REF: 60 kW, VSWR : ~ 2
2011campaign
2012campaign
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 7
Simulation on 3dB coaxial hybrid splitter
q Quadrant hybrid splitter
– when power is reflected from the resonant loops, the reflected power will go to the dummy load and will not be seen by the generator.
– S21, S31: -3.01 dB / S11, S41: -38.1 dB @ 30.8 MHz– S21, S31: -3.01 dB / S11, S41: -38.1 dB @ 30.8 MHz
– Phase difference (port 2 and 3): 90 deg.
-30
-20
-10
0
180
240
300
360
S11S21S31S41
S-pa
ram
eter
s (dB
)
Phas
e di
ffer
ence
(Deg
.)
input Output-3 dB
90 Deg.
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 8
-60
-50
-40
0
60
120
20 25 30 35 40
S41
S21-S31 (Deg.)S-pa
ram
eter
s (dB
)
Phas
e di
ffer
ence
(Deg
.)
Frequency (MHz)
30.8 MHz
Output-3 dBisolated
90 Deg.difference
Ultra-wideband 3dB coaxial hybrid splitter
q Proposed two-section 3dB hybrid splitter*
– Port 2&3: -3.10 ± 0.15 dB(amplitude)
– 90° ± 2° (phase difference)
– Bandwidth : 37% (proposed), VSWR < 1.3 -30
-20
-10
0Single-sectionTwo-sectionThree-sectionProposed circuit
Ret
urn
loss
(dB
)
– Bandwidth : 37% (proposed), VSWR < 1.3
-50
-40
-30
25 30 35 40
Ret
urn
loss
(dB
)
Frequency (MHz)
0.2
0.4
0.6Two-sectionThree-sectionProposed circuit
Am
plitu
de im
bala
nce
(dB
)
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 9
– *H. J. Kim et al., Applied Physics Letters 100 (2012) 263506-0.6
-0.4
-0.2
0
25 30 35 40A
mpl
itude
imba
lanc
e (d
B)
Frequency (GHz)
BW: 11.7MHz
Measurements on 3dB coaxial hybrid splitter
q RF measurement results
– S21, S31: -3.05 dB @ 30.8MHz
– S11, S41: -34.8 dB @ 30.8MHz
– Phase difference (port 2 and 3): 90.2 deg.– Phase difference (port 2 and 3): 90.2 deg.
-30
-20
-10
0
180
240
300
360
S11S21S31S41
S21-S31 (Deg)
S-pa
ram
eter
s (dB
)
Phas
e di
ffer
ence
(Deg
.)
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 10
-60
-50
-40
0
60
120
20 25 30 35 40
S21-S31 (Deg)
S-pa
ram
eter
s (dB
)
Phas
e di
ffer
ence
(Deg
.)
Frequency (MHz)
30.8 MHz
q Power measured at resonant loop A, B and hybrid splitter(HS)
– Total reflected power, P_total_ref = P_ref_A + P_ref_B
– Power ratio (P_HS/P_total_ref) becomes around 1à HS working is very good. (load resilient operation)
Load resilient operation with a hybrid splitter
good. (load resilient operation)
8
10
4
5P_HSP_total_ref
Ratio (P_HS/ P_total_ref)
ICR
F re
flect
ion
pow
er (k
W)
Ref
lect
ion
pow
er ra
tio
# 7899
15
20P_fwd_AP_fwd_BP_ref_H/SP_ref_AP_ref_B
ICR
F po
wer
(kW
)
# 7899
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 11
0
2
4
6
0
1
2
3
3 3.2 3.4 3.6 3.8 4IC
RF
refle
ctio
n po
wer
(kW
)
Ref
lect
ion
pow
er ra
tio
Time (s)
0
5
10
3 3.2 3.4 3.6 3.8 4
ICR
F po
wer
(kW
)
Time (s)
q Load resilient operation (200 kW, 1s) using a 3dB hybrid splitter
– Forward power: 200 kW, reflected power: 20 kW, averaged VSWR : ~ 2
– Stable operation of ICRF transmitter with 10% reflection (L–mode)
Typical load resilient ICRF operation
150
200
250
300
3
4
5
6ForwardReflected
VSWR
ICR
F po
wer
(kW
)
VSW
R
# 7398
90deg.àload resilient
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 12
0
50
100
0
1
2
6 6.2 6.4 6.6 6.8 7
ICR
F po
wer
(kW
)
Time (s)
àload resilient
q Load resilient operation in H-mode plasma
– Plasma density in the area of antenna changes rapidly in H-mode plasma
– The characteristic of wave propagation from antenna to plasma is affected
– High reflection from antenna plasma loading changed (high VSWR:2~6)
Stable ICRF operation in H-mode plasma
– High reflection from antenna plasma loading changed (high VSWR:2~6)
– Stable ICRF operation with a load resilient T/L in ELMy plasmas
3
4
5
6
6
8
10
12VSWR_loop AVSWR_loop B
Ratio
VSW
R
Rat
io (P
_HS
/ P_t
otal
_ref
)
# 7907
15
20
25P_fwd_AP_fwd_BP_ref_AP_ref_B
ICR
F po
wer
(kW
)
# 7907
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 13
0
1
2
3
0
2
4
6
6.5 7 7.5
VSW
R
Rat
io (P
_HS
/ P_t
otal
_ref
)
Time (s)
0
5
10
5 5.5 6 6.5 7 7.5 8
ICR
F po
wer
(kW
)
Time (s)
q Increase in the ICRF averaged coupled power in ELMy plasmas
– Effective protection of transmitter using a 3dB hybrid coupler
– Load resilient TL system leads to a stable power transmission in ELMy plasmas
– An effective load resilient operation is mandatory for reliable and efficient ICRF
Typical ICRF shot in ELMy plasmas
– An effective load resilient operation is mandatory for reliable and efficient ICRF power transmission
1000
1500
2000
2500
3000
600
800
1000
Ip (kA)NBI_total (kW)ICRF_forward (kW)ICRF_reflected (kW)
H_alphaW_TOT
NB
I (kW
), IC
RF
(kW
)
W_s
tore
(kJ)
, H_a
lpha
(a.u
.)
# 7273
200
400
600
800
150
200
250
300
Ip (kA)ICRF_forward (kW)ICRF_reflected (kW)W_TOT
H_alpha
ICR
F (k
W),
W_s
tore
(kJ)
H_a
lpha
(a.u
.)
# 7273
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 14
-500
0
500
1000
0
200
400
0 2 4 6 8 10 12
Ip (k
A),
NB
I (kW
)
W_s
tore
(kJ)
Time (s)
-400
-200
0
0
50
100
7.4 7.5 7.6 7.7 7.8 7.9 8 8.1
Ip (k
A),
ICR
F (k
W),
H_a
lpha
(a.u
.)
Time (s)
Conclusion
q We have newly installed a decoupler and a 3 dB hybrid coupler.
q Load resilient operation has been successfully performed in 2012 campaign.
– In L/H-mode plasmas, we found load resilient transmission line system – In L/H-mode plasmas, we found load resilient transmission line system leads to stable ICRF transmitter operation and high power transmission.
q We expect that the load resilient KSTAR ICRF system enables not only the stable transmitter operation but also enhancement of power coupling to the plasma in 2013 KSTAR campaign.
Japan-Korea Workshop Haeundae, Busan Jan. 28-30, 2013 15
q We also designed an ultra-wideband two-section 3 dB coaxial hybrid coupler by configuring asymmetric impedance matching using HFSS.
Thank you for your attention
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