Operational progress of 170GHz 1MW ECH system in KSTAR

8 th IAEA TM on Steady State Operation of Magnetic Fusion Devices, May. 29, 2015, NARA, JAPAN Operational progress of 170GHz 1MW ECH system in KSTAR J. H. Jeong a, Y. S. Bae a, M. Joung a, M. H. Woo a, S. H. Hahn a, H. Han a, S. W. Jung a, J. W. Han a, I. H. Rhee a, H. L. Yang a, J. G. Kwak a, Y. K. Oh a, H. Park a, M. Kwon a, K. Sakamoto b, K. Kajiwara b, Y. Oda b, J. Hosea c, R. Ellis c, W. Namkung d and M. H. Cho d a National Fusion Research Institute, Daejeon, Korea b Japan Atomic Energy Agency, Naka, Japan c Princeton Plasma Physics Laboratory, Princeton, USA d Department of Physics, POSTECH, Pohang, Korea E-mail : jhjeong@nfri.re.kr

OUTLINE Introduction Progress in conditioning for 170GHz gyrotron Upgrade activities of KSTAR ECH system in 2014 extension of pulse duration for 170GHz gyrotron upgrade of launcher mirror for Steady-state operation Summary Future plan -2-

Introduce: Layout of KSTAR ECH system in 2014 110GHz, loaned from GA (Aug. 2009) 0.3MW/2s (max.) Assisted startup & on-axis heating X2 mode at B T =1.4~2.4 T 1ch equatorial launcher with passively cooled mirror: 1MW/15s 170GHz, loaned from JAEA (Jun 2011) 1.0MW/50s (max.) on-axis heating & On/off-axis CD X2 at B T ~3.0 T, X3 at B T ~2.0 T Actively water-cooled mirror: 1MW SS (170GHz) Evacuated 63.5mm ID corrugated WG (~70m) -3-

Achievements of plasma current and pulse length in KSTAR since the First Plasma 2014 (1000kA, 17s, #11721) 2012 (900kA, 8s, #7200) 2011 (600kA, 12s, #6388) 2014 (600kA, 45s, #11660) 2012 (600kA, 20s, #7883) 2014 (500kA, 47s, #11664) 2010 (500kA, 5s, #3862) 2009 (320kA,#2048) 2013 (600kA, 21s, #9388) 2008 (100kA,#794) Since the first plasma, huge efforts To increase the plasma current toward MA and the pulse length toward 50 s as well 0.8MW 170GHz ECH (2011~ ) used as main ECH & supported long-pulse discharge of KSTAR Therefore, long-pulse operation of entire EC system required in 2014 0.4MW/2sed 84GHz ECH & 0.3MW/2sec 110GHz ECH used for pre-ionization & assisted startup 4-4-

170GHz gyrotron (TE31,12 mode) is working at NFRI June, 2011 @ JAEA July, 2011 @NFRI Sept., 2011 @NFRI -6-

Issue & Progress in conditioning for 170 GHz gyrotron since 2011 2011(0.75MW/10s/31%) Issue Installation & RF generation Action Investigation of operation parameters Successful demonstration of 170GHz EC beam to plasma 24% of flux saving by 0.6 MW 20-deg co-cd injection (et al., Jeong, FEC2012) -7-

Issue & Progress in conditioning for 170 GHz gyrotron since 2011 2011(0.75MW/10s/31%) Issue Installation & RF generation Action 2012 & 2013 (1MW/20s/40%) Investigation of operation parameters 5 sec. 20 sec pulse 1 sec. Issue High power & high efficiency Action Optimized parameter scan 2 nd beam & magnet alignment V_cpd (23 kv) V_anode (-5.5 kv) V_cathode (-49 kv) I_beam (~53 A) (curr. drop from 53 A to 45 A due to the cathode cooling) RF power -8-

OUTLINE Introduction Upgrade activities of KSTAR ECH system in 2014 - Progress of Gyrotron conditioning - Upgrade of ECH launcher mirrors - RT EC injection timing & mirror position control by PCS successful demonstration of NTM feedback control Summary Future plan -9-

Requirement and upgrade for 170GHz ECH in 2014 Requirements I. Long-pulse with high power injection (target operation was 50 sec) Upgrades (Enhancement of performance) Long pulse operation of Gyrotron with 1MW/50sec (collaboration with JAEA) Launcher mirror upgraded for steady-state operation with water-cooled mirrors (collaboration with PPPL) II. RT control of ECH power & target position (will be applied for NTM control) RT control of EC power (using anode control) & mirror position control implemented on KSTAR PCS (to apply MHD control) -10-

Issue & Progress in conditioning for 170 GHz gyrotron since 2011 2011(0.75MW/10s/31%) Issue Installation & RF generation Issue Action High power & high efficiency 2012 & 2013 (1MW/20s/40%) Investigation of operation parameters Action Optimized parameter scan 2 nd beam & magnet alignment 2014 (1MW/50s/40%) I_beam (~53 A) (curr. drop from 53 A to 45 A due to the cathode cooling) Issue in 2014 Limitation of pulse duration (due to cathode cooling effect) Action Anode voltage feed-back control Heater voltage control Development of water-cooled mirrors Main mode P j changes (mode conversion) by decrease of I beam dp dt j (P, P j 1 2 )V beam I beam P j -11-

Extension of pulse-duration at high-power regime (collaboration with JAEA) I. Anode voltage (V AK ) control at highest power condition # 103: V AK control # 106: No V AK control II. Pre-heating prior to pulse added to extend pulse length (with anode voltage control) # 129: w/o heater control # 139: heater control Power [kw] (@ V DETECTOR ) Mode shift Power [kw] (measured at diode detector) V AK : 44.4 45.6 kv V AK : no control V K : 48.0 kv V BODY : 24.0 kv V AK control V AK control I BEAM I BEAM 25 sec pulse Maximum pulse duration was 30 sec. Additional heater control required!! V HEAT : 25.7 V V HEAT : 28 V/30 sec over heating prior 1 minutes -12-

1 MW/50 sec operation of 170GHz gyrotron (collaboration with JAEA) (June 03, 2014) RF power: 0.8 MW avg. 53 A V AK control Beam current: not stabilized even for overheating during pulse Vac. Ion curr. 1.5 10-6 A max. RF power (calorimetric method) Dummy load 41 A 50 sec long-pulse operation at ~0.94MW (avg. power at the window) achieved by heater boosting (28 V) anode voltage control Total electrical efficiency is about 40 % Maximum collector surface temperature was ~150 degree with I BEAM ~ 50 A Calorimetric power measurement (all of water cooling temperature saturated) Channels T [deg.] Power [kw] Fraction [%] Dummy load 20 743 91% Pre-load 10 44 5.5% MOU chamber 12 18 2% Collector surface temp. Dc break 25 11 1% Window 0.7 1 0.5% V HEATER : 28V over heating during a pulse -13-

Upgrade of KSTAR ECH launcher (collaboration with PPPL, POSTECH & UNIST) Passively cooled mirrors (used until 2013): - collaboration with PPPL and POSTECH - 1MW for 15seconds, every 15 minutes - 0.8MW/10sec EC beam delivered to KSTAR (limitation of passively cooled mirror) Max. temp. increased to 91ºC for steering mirror [J. W. Han] Laser welding Upgraded with water-cooled mirrors in 2014: - 1MW for CW operation - 1.2MW 170GHz EC beam assumed for thermal analysis (190W/cm 2 Bessel squared heat flux distribution, 30W/cm 2 heat flux from plasma is assumed for steering mirror [R. Ellis, 2014 KSTAR conference]) - Brazing & welding techniques are used for fabrication of mirrors - Rectangular water coolant path enhance the cooling effect Water cooling pipe bellows fixed mirror Shutter steerable mirror Rectangular shape of water coolant path -14-

Successful operation of water-cooled mirrors for 2014 KSTAR plasma Max. Temp of MOU: ~50 C (ΔT~25 C) ECH: ~41 sec Saturation of ΔT Max. Temp of T/L: ~ 32 C (ΔT~10 C) KSTAR shot 10538 41 sec EC beam delivered to KSTAR to support the highβ & long-pulse operation of KSTAR T of water cooling for mirrors are saturated at 2.6ºC Power loss: 1.40kW (=190W/cm 2) for steering mirror & 1.28kW (=170W/cm 2 ) for fixed Heat flux from the plasma obtained using P of both mirrors and it was ~1.6W/cm 2 Delivered power of 0.8MW is estimated by absorbed power at the fixed mirror (0.16% of absorbed-fraction) Nominal surface temp. of T/L was 32 C ( T~10 C). Especially, MOU output port increased to ~50 C Further extension of the pulse width is possible with enhanced water cooling for T/L!! Measurement of surface temperature for T/L by TC sensors Gyrotron MOU TC sensors -15-

EC injection & mirror control by PCS (Heating Integrated control system) arbitrary modulation Power control system Change of injection time & modulation period in real time APS controlled by PCS to extract beam current which is the advantage of triode-gun ECE Mirror position scanning in poloidal -16-

Variation of injection angle & modulation freq. during a pulse KSTAR shot #10997 Pnbi ~ 2.4 MW, Pech ~ 0.75 MW (Off-axis X2 170 GHz co-eccd, Bt = 2.7 T) ECE [kev] <ne> Beam position change in poloidal at the resonance [cm] 17-17-

Demonstration of NTM control [et al., M. H. Woo] shot # 11313 Mode amplitude Critical amplitude shot # 10566 Critical amplitude Mode amplitude EC power injection MHD control start up Search & suppress Active q tracking Search & suppress algorithm is working correctly Active q tracking algorithm is working correctly Power is injected above the threshold amplitude -18-

Summary & future plan Long pulse operation of 170 GHz ECH/CD system in KSTAR Oscillation of 1MW for 50sec was obtained using V AK feed-back and Heater boosting Maximum pulse duration of 41sec EC beam delivered to KSTAR using newly developed water-cooled mirrors Saturation of temperature for gyrotron & launcher-mirror prospects to achieve more than 1MW 100sec. Successfully implemented EC power & mirror control system into the plasma control system -19-

Near-term future plan (before 2015 campaign) Target in 2015 (1MW/?? sec/40%) Advanced heater boosting scenario to achieve longer pulse operation with stable beam current Temperature monitoring system to measure the surface temperature of T/L will be prepared and water cooling jacket is under consideration Current water-cooled steerable mirror will be upgraded with flexible short-bellows type of mirror to avoid high-tension force from the water-pipes Current passive-cooled mirror will be replaced with new water-cooled mirror for steady-state operation -20-

Upgrade plan of KSTAR ECH system EC Power 2014 2015 2016 2017 170GHz, 1MW, 50s 170GHz, 1MW, 100s 105/140GHz, 1MW Launcher 1MW 2set 1MW 2set & Design of two beam launcher (2MW) Speed Motor design 10 degree/sec 170GHz, 1MW 105/140GHz, 2MW 1MW 2set & 2MW 1set (Fabrication of two beam launcher) 170GHz, 1MW (return to JAEA) 105/140GHz, 3MW 1MW 2set & 2MW 1set Fast moving system > 50 degree/sec > 50 degree/sec > 50 degree/sec Power cap. Steady-state Steady-state Steady-state Steady-state -21-

New 3 MW ECH upgrade plan E port Evacuated 31.75 mm ID 1MW SS (170GHz) corrugated waveguide (~40 m) + New 2-beam, 2 MW SS (105/140GHz) Evacuated 63.5 mm ID corrugated waveguide (~70 m) 110GHz/300kW(2s) N port 1MW SS (105/140GHz) Dash lines: New waveguides (63.5 mm ID) New 3 gyrotrons (1MW, 300 s, 105/140 GHz dual freq.) 170GHz/1MW(50s) Room for HV PS 105/140 GHz dual frequency for new ECH system 105 GHz for 1.8 ~ 2.2 T 140 GHz for 2.5 ~ 2.7 T (together with 170 GHz) 105/140GHz dual freq. gyrotron -22-

Thank you for your attention! National Fusion Research Institute realizes Green Korea getting joined with human beings, environment and technology 23-23-

Introduction: Mission of KSTAR The mission of the KSTAR is to develop a steady-state-capable advanced superconducting tokamak to establish a scientific and technological basis for an attractive fusion reactor (G.S. Lee, NF 41 (2001)) Long term operation plan of KSTAR (presented by Y. K. Oh) -24-

Repair of water-load I. Water leak at the rotating stem Worn-out of stem due to the friction between the seal and rotating stem 1 MW CW dummy load (loaned from JAEA)Pre-load ECH power Dummy load inside II. TiO2 coating melted away on the surface of dummy load -25-

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Issue & Progress in conditioning for 170 GHz gyrotron since 2011 2011(0.75MW/10s/31%) Issue Installation & RF generation Action ECH-assisted startup Gyrotron Matching optics unit T/L SCM Gun oil tank HV in -27-

Bellows -28-

Issue & Progress in conditioning for 170 GHz gyrotron since 2011 2011(1MW/10s/40%) 2012 & 2013 (1MW/20s/40%) 2014 (1MW/50s/40%) Issue Installation & RF generation Action ECH-assisted startup 24% of flux saving by 0.6 MW 20-deg co-cd injection -29-