Status of ICRF heating system and steady-state …psl.postech.ac.kr/kjw13/talks/Seki.pdfStatus of...
Transcript of Status of ICRF heating system and steady-state …psl.postech.ac.kr/kjw13/talks/Seki.pdfStatus of...
Status of ICRF heating system and steady-state experiment in LHD
T. Seki, T. Mutoh, K. Saito, H. Kasahara, R. Seki,G. Nomura and LHD Experiment Group
National Institute for Fusion Science,322-6 Oroshi-cho, Toki 509-5292, JapanJapan
Japan-Korea Workshops on Physics and Technology of Heating and Current Drive
Hanwha Resort, Haeundae, Busan, KoreaJanuary 28-30, 2013
Contents
• ICRF heating system and technology for • ICRF heating system and technology for steady-state operation in LHD- status of ICRF heating system
• long pulse plasma experiment in LHD- ICRF conditioning by 10 sec injection-- ICRF conditioning by 10 sec injection- recent result of steady state experiment
• Summary and future plan
Status of ICRF antennaPoloidal array (PA) antenna (HAS) antenna
Strap width30cm (PA)20cm (HAS)20cm (HAS)
Strap length70cm (PA, HAS)
Strap region3 ~ 73 cm (PA)-30cm ~ + 40cm (HAS)
Toroidal wavenumberk ~ 0 m-1 (PA)
In order to control toroidal wavenumber and reduce RF sheath loading on dipole excitationA handshake form antenna (HAS)“HA-SU-U” means wavenumber in Japanese.
k|| ~ 0 m-1 (PA)k|| ~ 7 m-1 (HAS)
Frequency38.47MHz
Protector (C, CFC)Cooling (water)Movable (~15 cm)
Experimental setup-ICRF heating antennas-
3.5U,L portHAS: hand shake antenna(Toroidal array antenna)(Toroidal array antenna)Capable of controlling k// with changing phase between applied RF power.Better heating efficiency
7.5U,L portPA antenna(Poloidal array antenna)Better loading resistance
# 1 IPA
# 2 IPA
# 1 DPA
# 2 DPA
# 1 FPA
# 2 FPA
Im pedance
m atching
device
Impedance
m atching
3 .5 U
Antenna
3 .5 L
~ 4 kW ~ 1 0 0 kW ~ 1 MW
Hall for Heat ing Devices Basem ent
of LHD
LHD Hall
Six steady state transmitters can be operated simultaneously
RF transmitterLiquid stub tuner Antenna
CPI
CPI# 2 IPA
# A IPA
# 2 DPA
# A DPA
# 2 FPA
SG
m atching
device
Im pedance
m atching
Antenna
4 .5 U
Antenna
4 .5 L
Antenna
7 .5 U
# 5 A FPA
# 3 IPA # 3 DPA # 3 FPAIm pedance
m atching
device
# 4 IPA # 4 DPA # 4 FPA
Im pedance
m atching
device
installed in near future
CPI
Thales
Eimac
# A IPA
# B IPA
# A DPA
# B DPA
# 5 B FPA
# 6 B FPA
m atching
device
Impedance
m atching
device
Antenna
7 .5 L
Antenna
IPA: Intermediate Power Am plifier
DPA: Driver Power Am plif ier
FPA: Final Power Am plif ier
# 6 A FPA
5changeable from 25 to 100 MHz
Thales
Thales
Eimac
Operational test of RF transmitters were carried out using steady state dummy load
•#1: 4CM2500KG– =>3.5U antenna– 0.55MW / 1h
0.8
1.01GJ 2GJ
– 0.55MW / 1h
•#2: 4CM2500KG– =>3.5L antenna– 0.54MW / 1h
•#6A: TH525A– =>7.5U antenna– 0.52MW / 0.5h– 0.23MW / 1h0.2
0.4
0.6
0.8
RF
Pow
er [M
W]
#1#2#6A
#6B
0.1GJ
– 0.23MW / 1h
•#6B: TH525A– =>7.5L antenna– 0.49MW / 0.5h– 0.24MW / 1h
•Total input energy: 6 GJ
0.0
0.2
100 1000 10000Time [s]
achieved in 2007
Stub3Stub2Stub1
Automatic impedance feedbackcontrol by Liquid stub tuner
Time evolution of liquid length of stubDouble or triple stub configuration
1.4
1.5
gth[
m] Oscillator Side
Time evolution of reflectivity
1.1
1.2
1.3
0 500 1000 1500 2000
Liqu
id L
eng
Time[s]
Antenna Side
•Necessary for steady state operation•Applicable from several sec to CWoperation•Automatic control of antenna phase is also introduced for HAS antenna
Real-time phasing system is installed
114021 Phase (I,Q)Antenna loading has time evolution in a short time.Impedance matching changes with the antenna phase, and the antenna phase changes impedance matching.
The difference for the time evolution is not so large at the initial phase in short time discharge, and there is no guarantee for keeping phase in the discharge.
In order to achieve effectively phasing experimentsthe real-time impedance matchingthe real-time phase feedback
114039 Phase (I,Q)the real-time phase feedbackkeeping forward power in various antenna loadingare needed.
Stable current phasing is demonstrated in the LHD, and accurately phasing experiment is able to be carried out.With phase feedback
Experimental condition for ICRF heating
- minority ion heating -• Magnetic field and axis are B=2.75T, Rax=3.6mare B=2.75T, Rax=3.6m
• Wave frequency: 38.47MHz
• He plasma mixed with minority H ionsminority H ions
• Ion cyclotron resonance layers are located at saddle point of magnetic configuration
ICRF discharge was used for plasma conditioning
IAEA2012 by H. Takahashi
• Repeated 10 sec ICRF discharge decreased the hydrogen minority ratio
–ECH assist is effective in high minority situation at the beginning of conditioning
–useful for remove the hydrogen from helium plasma• Electron density profile changed from hollow to flat or center-peaked
–contributed for high ion temperature achievement
Highest ion temperature was achieved after ICRF conditioning
IAEA2012 by H. Takahashi
• High ion temperature was obtained • High ion temperature was obtained after ICRF conditioning
• Change of electron density profile led to increase of Pi/ne
Plasma parameters of SSO is steadily improved
• HAS (dipole mode) antenna has better antenna has better performance than HAS (monopole) and PA antennas.
• Plasma density was increased almost proportionally to Pproportionally to PRF
(PICH+PECH).
Highest density ICRF plasma was achieved
ne=3.6x1019m-3 with PRF~2.4MW for 10s
•High density plasma with ne=3.6x1019m-3 , Te~Ti~1keV ne=3.6x1019m-3 , Te~Ti~1keV and Wp=300kJ was sustained with PICRF=2MW and PECH=0.37MW for 10 seconds.
•Plasma parameters were constant after 5 seconds.constant after 5 seconds.•could be extended more.
Steady state operation by minority ion heating was successfully carried out
discharge time: 54min and 28sec, average input power: 490kW
• Power control during plasma discharge with watching sparks in vacuum vessel
• Rax=3.64-3.67m, ne~0.4x1019m-3, Te~Ti~1keV• Plasma was terminated by sudden increase of density
caused by influx of iron impurity
Long pulse operation was carried out with high density and high RF power
ne=2.4x1019m-3 with PRF~1.8MW for 60s
•Plasma of higher density with higher RF power was higher RF power was sustained for 60 sec.
•The long pulse operation was extended to the new region of duration time vs. PRF.
Fusion triple product :nôETi~3.5x1018m-3 sec keV
Longest pulse discharge with 1x1019m-3
•pulse length: 18min. 55sec. (1135sec.)
•total ICRF power: 0.7MW- 3.5U: 0.22MW- 3.5U: 0.22MW- 3.5L: 0.22MW- 7.5L: 0.27MW
•ECH power: 0.27MW
•antenna-plasma gap- 3.5: 7.5cm- 3.5L: 12.5cm
•line-averaged electron 19 -3
•line-averaged electron density: 1x1019m-3
•highest temperature at 7.5 antenna is higher than that of 3.5 HAS antenna
Movie for 19 min. discharge
tangential view of 7.5 PA antenna From 3.5L to upper From 3.5U to lower
From 7.5U to lower
Discharge was terminated with spark around 7.5 PA antenna
tangential view of 7.5 PA antenna From 3.5L to upper From 3.5U to lower
From 7.5U to lower
Observing a spark event with low minority ratio
• A spark event is happened with low H minority ratio afterrepeated steady-state operation.
• By injecting hydrogen super sonic gas puffing (SSGP), the spark event is reduced and vanished in a few minutes(approximately 2 minutes in this discharge after SSGP(0.01Pa・m3/s)).
One of the candidate of sparking place
LightLight
• The spark position is not confirmed, but it seems to be outside at next port by the light of sparks. (flakes on divertor tiles ?)
• As RF power for the PA antenna is increased, the sparks is easy to be happened.
• Checking the relationship between the accelerated tail and this spark.
From 3.5L From 3.5U
Red light emission of divertor trace on the carbon plate protecting coaxial line of ICRF
Carbon plate was curved
From 7.5U
protecting coaxial line of ICRF antenna
From 7.5U
Curved surface of carbon by divertor legWater leak occurred at the support of the carbon plate(7.5L PA antenna)
Summary of recent long pulse discharges
• Density is different in year by year:
• former exp.: less than 19 -3
Duration Time vs. PRF
• former exp.: less than 1x1019m-3
• 2011: more than 1x1019m-3
• 2012: about 1x1019m-3
• extend pulse length in injection of MW level and density of 1x1019m-3
• Spark is still important issue for steady state operation
• Sparks from HAS (dipole mode) antenna is a little
temporary
Summary and future plpan• ICRF discharge was useful for plasma
conditioning
• Reduce H ratio, modify density profile • Reduce H ratio, modify density profile
• Higher density was achieved by HAS antenna with PA antenna
• 1019m-3 plasma was sustained about 19 minutes by ICRF heating and ECHby ICRF heating and ECH
• New antenna will be installed in next campaign
- PA type antenna aiming at high power injection