ICRF Physics in KSTAR Steady State

Transcription

1 ICRF Physics in KSTAR Steady State Operation (focused on the base line operation) Oct. 24, 2005 Jong-gu Kwak on the behalf of KSTAR ICRF TEAM Korea Atomic Energy Research Institute

2 Contents Roles of ICRF at KSTAR ICRF system development and its present status Physics issues of ICRF

3 Roles of Heating & CD System at KSTAR Multiple heating technologies based on neutral beam, the ion cyclotron waves, and the lower hybrid waves and the electron cyclotron waves provide Heating and current drive capability for long pulse length up to 300 sec. Flexibility in the control of current density and pressure profiles for advanced tokamak plasmas The NBI system provides ion heating & current drive, current and pressure profile control, core fueling, and plasma rotation. The ICRF system provides heating, centrally peaked current drive, and off-axis current drive using mode-conversion. - bulk heating and CD by FW - localized CD and electron heating by MC The lower hybrid system provides off-axis current-profile control, efficient bulk current drive at low plasma temperatures, and electron heating. The ECH system will be used at the day one operation of the KSTAR to aid plasma breakdown for plasma initiation, and will be upgrade to 1 MW ECCD system for MHD stability and improved core transport

4 Comparison of heating power with other devices R(m) A(m) k Bt (T) I (MA) Configuration P-NBI (MW) P-LH (MW) P-ECH (MW) P-ICRF (MW) Asdex-U P-diverter DIII-D P-diverter KSTAR P-diverter 8(14) 1.5(3) 1 6(12) Toresupra E-diverter TEXTOR E-diverter 6 2 HT We hope to extend the present AT researches more wide(βn 5) with 300 sec by controlling pressure/current profiles and MHD instabilities at real time basis

5 A self consistent analysis of MHD equilibrium and current distribution Operation space at KSTAR (reverse shear) < li < 1.3(High li) <βn<5.0 It is important to assure that those configuration can be achieved with H/CD system under development. NCT AT ACCOME code is used - density and temperature profile is assumed - Fully non-inductive operation modes (baseline, upgrade, reverse shear mode) 1-1/2 transport simulation code WHIST is used to assure the equilibrium pressure that we assumed in ACCOME simulations. KSTAR FIRE Inductive

6 Reference mode (baseline) Current density (A/m 2 ) 2.0x10 7 Total NBI 1.5x10 7 Bootstrap Lower hybrid Fast wave 1.0x x Poloidal flux Safety factor Poloidal flux (solid), Square-root toroidal flux (dotted) -1.47MA with P-NB= 8 MW, P-LH= 1.5MW, P-FWCD= 6.0 MW - ne(0)= m-3, Te(0)=Ti(0)= 10 kev. - The volume-averaged βt and βp are 1.76% and 1.38 %, respectively.

7 Upgrade Reference Mode Current density (A/m 2 ) Total NBI 6.0x10 6 Lower hybrid Fast wave Bootstrap 4.0x x10 6 Safety factor Poloidal flux Poloidal flux (solid), Square-root toroidal flux (dotted) - 2MA with P-NB= 18 MW, P-LH= 1.0MW, P-FWCD= 0.5 MW(P-ICRF=8.5MW) - ne(0)= m-3, Te(0)=Ti(0)= 14 kev - High Beta is limited by high-n ballooning instability - βt and βp are calculated as 3.75 and 1.7%, respectively.

8 Reverse Shear Mode Current density (A/m 2 ) 2.5x10 6 Total 2.0x10 6 Bootstrap Lower hybrid 1.5x x x Poloidal flux Safety factor Poloidal flux (solid), Square-root toroidal flux (dotted) MA with P-LH= 2.85MW(bootstrap current =1.72 MA) (P-NBI=20MW, P-ICRF=12MW and P-LHH=1.65MW) -β N =5.2(βt and βp are calculated as 6.2 and 2.5%, respectively, - ne(0)= m-3, Te(0)=Ti(0)= 16 kev - negative current drive using NBI or FWCD can be used to optimize the q profile for MHD stability. (*)Further revise is required.(flh=3.9ghz)

9 Review of ICH/CD contribution to KSTAR P-NBI P-LH P-ICRH P-FWCD (MW) (MW) (MW) (MW) Baseline Upgrade Reverse shear FWCD is very important during the baseline period FWCD contribution to KSTAR is decreased for reverse shear mode period because most of current is derived from bootstrap currents IC Heating plays the major role in upgrade/reverse shear mode Localized CD and electron heating using MC plays an important role in reverse shear mode

10 Heating and CD Scenarios H minority heating in D majority plasma or second harmonic heating of D: ~ 50 MHz at B 0 =3.5 T ~ 36 MHz at B 0 =2.5 T Ion cyclotron resonance frequencies for B 0 =3.5 T 90.0 R0-a B0 = 3.50 T R0+a Fast Wave Current drive in D majority plasma with H minority: ~ 38 MHz at B 0 =3.5 T ~ 27 MHz at B 0 =2.5 T Off-axis Current drive in D majority with He 3 minority B 0 =3.5 T: Operation between MHz may be possible for He 3 minority heating or off-axis current drive using mode conversion D 2 He3 H, 2D, 3T He3, 2T D By changing phase difference between current straps, simple change from CD to heating is possible T Major radius (m)

11 On/Off axis CD - Low density and high Te - about 390 ka can be driven at ne(0)= m-3, Te(0)=10 kev, Ip=1.5 MA and q0=1.3, - CD efficiency= A/W-m2. - TORIC/TASKW1 - central peaked current profile.-mccd driven-current profiles corresponding to =38, 35, 32, and 30 MHz (with 20% He 3 /D majority at Te(0)=2 kev and ne(0)= m-3) -Frequency and Concentration changes -FELICE/TASKW1

12 System development and its present status

13 Deliver full power at any frequency in the MHz range with the peak voltage < 35 kv. Be able to adjust inter-strap phasing to any value from -π to +π. Can be upgraded to deliver 12 MW for 300 sec pulses. Four current straps antenna A resonant loop with two line-stretchers. A decoupler between the end strap circuits. A matching system; a line-stretcher and a stub tuner. Main transmission line; 3 atm N 2, water/air-cooled A combiner/splitter circuit (Possible upgrade option) 4 x 2 MW RF power sources tune MHz Distinct features System Design ICRF System Design PS2MWOptionalUpgradeVTDBSTPSDLDecouplerSTPSDL2MW2MW2MWStrap1Strap2Strap3Strap4ELMDumpLegend DB : DC Breaker DL : Dummy Load PS : Phase Shifter ST : Stub Tuner VT : Vacuum Transmission Line 61/8"line93/16"lineVacuumVesselKSTARTokamakHallHeatingRoom

14 Voltage in resonant loop < 35 kv will deliver 6 MW to plasma Physics calculations of R'(plasma loading): Freq. (MHz) Mode R'(Ω/m) 27 FWCD (2.5 T) FWCD (3.5 T) Heating (3.5 T) 7.4 -With lossy transmission circuit model of antenna and resonant loop, can calculate current and voltages needed to deliver 6 MW to the plasma. -RANT3D calculates loading resistance -Note that this is based on the vacuum condition, if we consider the plasma environment, we should increase the voltage standoff capability up to about 50 kv. Voltage [kv] Strap f=50 MHz f=27 MHz f=38 MHz Current [ka] Strap f=50 M Hz f=38 M Hz f=27 M Hz Distance from strap center [m] Distance from strap center [m]

15 RF Transmitter (30 MHz, 100 kw) Antenna test setup Vacuum Feedthrough Top-side Line Feeding Line RF Test Chamber (ICRF Antenna Installed) 17 m Bottom-side Line Stub Tuner

16 Major Shots : Achieved in Vacuum The high-voltage and longpulse capabilities were significantly enhanced by adapting an active watercooling system. Achieved standoff voltages are 41.3 kvp for a pulse duration of 300 sec, and 46.0 kvp for 20 sec, which exceed the design requirement of 35 kv for 300-sec duration. Nevertheless, we should increase a standoff voltage to a higher level, because a standoff voltage achieved in vacuum may be degraded in plasma environment. In addition, HV test for two/four strap is needed.

17 Physics issues on the first plasma and the base line operation

18 System Development and operation plan at KSTAR - 1/2 Set (3MW) by Launcher Trans Line Sys Transmitter Eng. Design. Eng. Design Prototype Antenna Fabrication & Test Antenna Components Development Eng. Design Control/Arc Detector R&D High Power, Long-pulse RF Components -Tuners - Transmission components Transmitter R&D 2 MW Transmitter 1 Set Assembly Finish Install & Test (plasma) ICRF-heated Plasma Antenna Fabrication 1/4 set 2/4 set 1.5MW 3MW 4/4 set (?) Fabrication & Install Proto. Ant. Install (?) Antenna/chamber conditioning Assistant in plasma start-up 4 MW ready 2 MW Transmitter 3 Set 8 MW ready (?)

19 Physics issues at near term Near term Not preparing diverter and PFC for high power operation until High beta operation requires strong shaping of plasma so that operation of diverter is required -PFC components should be prepared Plasma startup assistance - reduce the volt-second requirement for PF - ICRF assist startup - weak point : high line voltage on the antenna at vacuum loading condition Nominal electron/ion heating for the circular shape plasma - redesign of front surface of antenna - CD efficiency is proportional to Te - At the initial period without NBI, Te is very low - pressure profile control by ICRH or FWEH - weak point : interaction of RF with wall due to lack of low Z PFC at wall and single pass absorption is low Discharge cleaning - a difficulty in conventional discharge cleaning at permanent magnetic field due to the plasma instability.

20 ICRF assistance to startup at KSTAR RF assistance startup is very important at superconducting tokamak. - reduce volt-sec requirement for PF coils - ITER will use ECH startup At the initial period of KSTAR operation around Nominal toroidal field(3.5t) of KSTAR might not be used because conditioning of superconducting magnet is required GHz source that we already had is not effective because it is in the second harmonic heating region at 1.5-2T. - Heating efficiency is degraded for fundamental/second O and second harmonic X due to finite Larmor radius effects. ICRF assist plasma startup could be an another option - TEXTOR-94 (2Ωci scenario, 32MHz, 2.24T, Prf= kW) : Eparallel is reduced from 0.45 to 0.32 V/m : Note that this was done at ICRF antenna without faraday shield - HT7 (2Ωci scenario, 30MHz, 1.8T, Prf(350kW)=150kW(ICRF)+200kW(LH)) : Eparallel is reduced from 2.5 to 0.5V/m : Note that this was done with ICRF + LHW power Candidate for RF assistance to plasma startup at KSTAR -ECH(Second harmonic/500kw)+icrf(200kw)

21 Transmission line configuration(i) at near term DCB1-U STRAP1 DCB1-B DCB2-U STRAP2 Signal Gen. Power Amp DCB2-B Phase 2 MW DCB3-U STRAP3 DCB3-B Driving Four current straps at fixed frequency Second harmonic heating of H at 2T : 60 MHz 0/180/0/180 phase Coupled power : 1.5 MW No line stretchers and decouplers Reduce the line voltage on the resonant loop down to 17kV DCB4-U DCB4-B STRAP4

22 Transmission line configuration(ii) at near term DCB1-U STRAP1 DCB1-B DCB2-U STRAP2 Signal Gen. Power Amp DCB2-B Phase 2 MW DCB3-U STRAP3 DCB3-B DCB4-U STRAP4 Driving Four current straps at fixed frequency Second harmonic heating of H at 2T : 60 MHz 0/180/0/180 phase Coupled power : 1.5 MW No line stretchers and decouplers line voltage is reduced on matching system more than that at configuration I More reliable(?) than I power divider and dummy load(3 set) More DC break and stub are needed DCB4-B

23 Physics issues at long term (after 2009) Long term after installing diverter and passive stabilizer Workhorse for AT plasma with steady state operation -Direct current profile control using FWCD and MCCD -Pressure control by way of ICRH or FWEH He 3 minority heating : attractive scenario for ITER activated plasma ITER Hybrid scenario development at T i T e NBI Ti, FWEH Te plasma rotation during ICRF heating Investigation of AE activity using high energy ions up to MeV driven by ICRF - alpha particle driven TAE instability may be a substantial loss of hot fusion born alpha particle

24 Thank you very much