National Fusion Research Institute. Pohang, Korea, December 14-16,

Transcription

1 Korea-Japan Workshop on Physics and Technology of Heating and Current Drive Hyunho Wi, Haejin Kim, Sonjong Wang, and Jong-gu Kwak National Fusion Research Institute Pohang, Korea, December 14-16,

2 Contents I. Introduction Basic properties of Traveling Wave Antenna(TWA) Combline filter based TWA II. Antenna design and EM simulation results of TWA Antenna design parameters Coupling and load resiliency Parallel refractive index (n ) III. Fabrication and measurement results of TWA IV. Status of KSTAR Helicons RF system V. Summary and future work <2/14>

3 Introduction Basic properties of Traveling Wave Antenna(TWA) <Simple circuit model of a TWA> MM = MMMMMMMMMMMM rrrrrrrrrrrrrrrrrr RR = SSSSSS oooo ooooooooo llllllll iiii ttttt llllllll aaaaaa rrrrrrrrrrrrrrrrrr llllllllllllll RR ωωmm, nn(nnnnnnnnnnnn oooo llllllll) ZZ iiii = ωωmm RR + 8 ωωmm ZZ iiii ωωmm Input impedance(z in ) is nearly independent of resistive loading load resiliency TWA enables tuner-free antenna system TWA based combline filter had shown good performance in JFT2M tokamak Vacuum feedthroughs(vft) need only at both end of feed and termination <3/14>

4 Introduction Combline filter based TWA P t (Transmitted Power) Gap P f (Forward Power) Radiator L P r (Reflected Power) M R C <Illustration of combline filter based TWA> LL = IIIIIIIIIIIIIIIIIIII CC = CCCCCCCCCCCCCCCCCCCCCC MM = MMMMMMMMMMMM rrrrrrrrrrrrrrrrrr RR = SSSSSS oooo ooooooooo llllllll iiii ttttt llllllll aaaaaa rrrrrrrrrrrrrrrrrr llllllllllllll TT = PPPP PPPP = VVVV VVVV 2 2 RR = PPrr PPPP = VVrr VVVV AA = 1 (TT + RR) The performance of the TWA can be defined by the transmission coefficient T, reflection coefficient R, and sum of radiation and absorption coefficient A. <4/14>

5 Antenna design and EM simulation results of TWA 3D structure of TWA Poloidal P out Radial toroidal P in Alumina Insulator Faraday Shield Operation frequency: 500 MHz Number of radiators: 10 Radiator Dimension: 600mm x 180mm x 54mm Gap between radiators: 50 mm 5inch Coaxial line <5/14>

6 Antenna design and EM simulation results of TWA EM simulation results with vacuum loading 0-5 TT MHz S-parameters (db) RR 0-35 S 11 (Simulation) S 21 (Simulation) Frequency (MHz) AA 0 Power Spectrum (a. u) Pallell refractive index (n ) Operation frequency: 500 MHz Peak n ~ 3 BW: ~25 MHz d : 100 mm (180 degree phase) <6/14>

7 Antenna design and EM simulation results of TWA EM simulation results with resistive(plasma) loading 0 gap Sea Water S-parameters (db) S 11 Vacuum S 11 Gap=10mm S 11 Gap=20mm S 11 Gap=30mm -30 S 21 Vacuum S 21 Gap=10mm S 21 Gap=20mm S 21 Gap=30mm TT 0.1~0.2 RR 0 AA 0.8~0.9 (εε rr = 7777, σσ = [ ss mm ]) Frequency (MHz) Simplified plasma modeling by using the sea water, the performance of TWA is simulated. Depending on the gap between antenna and plasma, the reflection(s 11 ) is nearly independent load resiliency. Coupling between antenna and plasma(s 21 ) can be easily controlled by changed the gap. <7/14>

8 Antenna design and EM simulation results of TWA EM simulation results with resistive(plasma) loading Feed Termination Diagnostic line Termination E-field Feed Ey(re)field [V/m] Feed Toroidal direction (mm) Termination Absorption of plasma is indirectly simulated by MSW CST. gap=10mm The strength of electric field along with the diagnostic line, is gradually decreased. Sea Water (εε rr = 7777, σσ = [ ss mm ]) <8/14>

9 Fabrication and measurement results of TWA The components of TWA is made of copper The front surface of faraday shield is coated with tungsten TWA is installed in KSTAR p-port 30cm above the mid-plane Both sides of TWA in the toroidal direction were protected by graphite poloidal limiters The radial position of the front surface of the faraday shield was 0.5cm behind the front surface of the poloidal limiters <9/14>

10 Fabrication and measurement results of TWA Measurement results 90 degree 6-inch coaxial elbow 0-5 S-parameters (db) S 11 (Simulation:TWA) S 21 (Simulation:TWA) -35 S 11 (Measurement:TWA+VFT) S 21 (Measurement:TWA+VFT) Frequency (MHz) TWA The measurement of TWA was performed using VFT a two-port vector network analyzer Agilent E5071C The measurement results includes the properties of TWA, VFT, and elbow. <10/14>

11 Status of KSTAR helicons RF system Diagram of KSTAR Helicons RF system TWA Dummy load V F T V F T Attenuator Att. P/S Pre-amp(50w) Klystron Phase shifter Klystron(75kW) 3 6 inch DC Block Att. P/S Preamp Klystron 3 6 inch Circulator SG 4way-power divider Hybrid Power Combiner Att. P/S Klystron Preamp 3 6 inch Att. P/S Klystron Preamp 3 6 inch Dummy load Dummy load <11/14>

12 Status of KSTAR helicons RF system Illustration of KSTAR Helicons RF system ICRF TWA Circulator Water-load KSTAR(P-port) Hybrid Power Combiner Klystron <12/14>

13 Status of KSTAR helicons RF system Picture of KSTAR Helicons RF system VFT Directional coupler Circulator Water-cooled type dummy load RF power Klystron <13/14>

14 Summary and future work TWA for helicons is designed based on the combline filter theory. RF EM Simulations, fabrication, and RF test of the TWA were done in Coupling could be easily controlled by changing radial outer gap between antenna and plasma without dependent of reflection coefficient. ~120kW combined RF power is obtained by using the two of klystrons. Helicons RF heating system at 500MHz was installed for verification of helicon wave heating and current drive experiments at the KSTAR. High power helicon wave current drive will be test and analyze. <14/14>

15 Thank you for your attention

16 Combined RF Power Combined Power Dummy Power Klystron Pout (kw) Mechanical Phase Shifter Value (a.u)

17 Prototype TWA for high power is designed Comparison of two TWAs Mock-up (2015) Prototype (2016) Frequency ~ 500 MHz ~ 500 MHz Bandwidth ~ 20 MHz ~ 40 MHz Antenna Type Combline filter based TWA same <Mock-up TWA, 2015> Feeding type 3.5 mm SMA 6-1/8 inch Coaxial Input Power 1 mw (VNA) 200 ~ 300 KW (4 klystrons) Peak n ~ 3 ~ 3 Antenna length 600 mm 600 mm KSTAR Conference, Feb. 2016, Daejeon <Prototype TWA, 2016> 17

18 Simulation results of prototype Helicon wave TWA EM simulation results Design frequency: 500 MHz Peak n ~ 3 BW: ~40 MHz d : 100 mm (180 degree phase) gap between current straps: 50 mm Prototype Helicon Wave TWA S-parameters (db) Power Spectrum (A.U) S 11 S Frequency (MHz) n KSTAR Conference, Feb. 2016, Daejeon 18

19 Key components of high power Helicon wave current drive system are designed, fabricated and RF tested Coaxial window: simulation & rf test Window 500 MHz S 11 : - 48 db (sim.) - 34 db (test) S 21 : db (sim.) db (test) - Very good agreement KSTAR Conference, Feb. 2016, Daejeon 19

20 Key components of high power Helicon wave current drive system are designed, fabricated and RF tested Power combiner: simulation results 3λ/ teflon 5λ/4 3 1 (klystron) MHz S 61 : db S 62 : db S 63 : db S 64 : db MHz S 11 : - 18 db S 21 : db S 31 : db S 41 : - 18 db dummy 7 dummy KSTAR Conference, Feb. 2016, Daejeon 20

21 Key components of high power Helicon wave current drive system are designed, fabricated and RF tested Power combiner: fabrication & rf test 1 st MHz S 11 : - 17 db S 21 : db S 31 : db S 41 : - 16 db 2 nd test after cutting of T.L (5 500 MHz S 11 : - 19 db S 21 : db S 31 : db S 41 : - 19 db 3 rd test after welding (low loss) KSTAR Conference, Feb. 2016, Daejeon 21