Introduction of 6 th Steady State Operation ITPA Topical Group Meeting X.D. ZHANG

Introduction of 6th Steady State Operation ITPA Topical Group Meeting X.D. ZHANG 8-10 November, 2004 IST, Lisbon, Portugal

6th SSO ITPA Meeting Participants (28/10/04) US Tim Luce luce@fusion.gat.com Peter Politzer politzer@fusion.gat.com Ron Prater prater@fusion.gat.com Roger Raman raman@aa.washington.edu Randy Wilson jrwilson@pppl.gov EU Claude Gormezano gormezano@frascati.enea.it Rob Akers rob.akers@ukaea.org.uk Alain Becoulet alain.becoulet@cea.fr Gerardo Giruzzi gerardo.giruzzi@cea.fr Didier Moreau Didier.Moreau@jet.efda.org JM Noterdaeme jmn@ipp.mpg.de George Sips ccs@ipp.mpg.de Angelo Tuccillo tuccillo@frascati.enea.it

6th SSO ITPA Meeting New membership EU:A.Becoulet, C.Gormezano, A.C.C.Sips, A. Tuccillo Japan:S.Ide, A.Fukuyama, K. Hanada, T.Suzuki, Y.Takase, Y.Nakamura RF: V.Kulygin,V.Vdovin, A.Zvonkov US: C.Philips, P.Bonoli, C.Forest, W.Heidbrink, R.Prater China: X.Gong, X. Ding, X. Zhang, X.Song, J.Luo Korea: K.I.You, Y.S.Na, J.M.Kwon ITER: T.Oikawa up to 9 November 2004 Chair&co-chair: C. Gormezano & S. Ide after 9 November Chair&co-chair: A.C.C. Sips & S. Ide

6th SSO ITPA Meeting Participants (28/10/04) Japan Shun Ide ide@naka.jaeri.go.jp Kazauaki Hanada hanada@triam.kyushu-u.ac.jp Yukio Nakamura nakamura.yukio@LHD.nifs.ac.jp Hiroschi Idei idei@triam.kyushu-u.ac.jp Yuichi Takase takase@plasma.phys.s.u-tokyo.ac.jp Takahiro Suzuki suzukit@fusion.naka.jaeri.go.jp Atsushi Fukuyama fukuyama@nucleng.kyoto-u.ac.jp China Xiaodong Zhang xdzhang@ipp.ac.cn ITER Toshihiro Oikawa toikawa@naka.jaeri.go.jp

6th SSO ITPA Meeting Charter for the:Steady-State Operation Topical Group Explore the potential for achieving integrated scenarios for steady state operation in a burning plasma experiment: Scenarios for steady-state operation and maximising fusion energy produced Control systems (NB, ICH, ECH, LH, fuelling, pumping, …… Applicability, feasibility and compatibility of heating and current drive, fuelling, particle exhaust and angular momentum injection systems, forintegrated operation in ITER. Steady state burning plasma conditions and techniques for current profile, density, and performance control (beta, fusion power….).

6th SSO ITPA Meeting S. Ide: IAEA Highlights on Steady State scenarios T. Luce: IAEA Highlights on Hybrid scenarios Joint meeting with Transport Group on Joint experiments (SSOEP1 & SSOEP2): achieved results JT-60U (S. Ide) AUG (G. Sips) DIII-D (T. Luce) JET (X. Litaudon) Joint meeting with Transport Group on Joint experiments (SSOEP1 & SSOEP2): proposals for new experiments, fill in the bullets

6th SSO ITPA Meeting Heating & Current Drive R. Prater: IAEA Highlights on Heating &CD H. Idei: Initial results on ECCD hardware experiments on TRIAM-1M R. Prater: Status report on ECCD code benchmarking E Joffrin: IAEA Highlights on Control Issues D. Moreau: Control of ITBs on JET T. Suzuki: real time control of j(r) in JT-60U Joint meeting with Pedestal Group G. Sips: Pedestal issues in Steady state and hybrid scenarios

6th SSO ITPA Meeting (distance between the two separatrices at the midplane of diverted plasmas) organised byR. Stambaugh AUG L. Horton or A. Kallenbach DIII-DE. Strait JT-60UN. Asakura C-MODA. Hubbard MAST H. Meyer NSTXR. Maingi

6th SSO ITPA Meeting Joint meeting with Modelling group: presentations R. Budny: simulation of heating &CD in ITER A. Becoulet: latest ITER current profile simulation for ITER with CRONOS A. Fukuyama: latest ITER current profile simulation for ITER with TASK M. Murakami:latest current profile simulation for ITER with ONETWO Joint meeting with Modelling group: Nuclear Fusion paper Steady state operation K. Hanada: Impurity accumulation and expulsion in a TRIAM-1M long pulse discharge P. Politzer: Is a “steady-state" plasma necessarily stationary?

Integration: meaning? 6th SSO ITPA Meeting From JT-60U: Integrated performance <=> the ITER steady state domain • Shall we add items: • Pedestal • Impurity accumulation • Divertor compability • Others?

6th SSO ITPA Meeting

Experiments in 2004 at ASDEX-U • AIMS: • q-profile evolution in Hybrids, and MHD. • Operation at 600kA/1.4T and 1.2MA/2.8T. • Variation in q95(and density) in collaboration with DIII-D. • ICRH heating with PICRH > PNBI

Still to be done on ASDEX-U..... • Physics: • Scaling of the confinement with b and r* and stability (r*,MHD). • Document the edge of the plasma. • Scaling to ITER. • Operation at high density, small ELMs ? • Scenario development: • Use of ICRH, towards on RF only demonstration. • Use of ECCD for q-profile and MHD control. • Demonstrate at q95 ~3 or lower. • Assess operation at low density with increased W surface. • Integration: • ELM control techniques with improved confinement. • International collaboration.

6th SSO ITPA Meeting Joint experiment 2005 Steady-State Operation current profile q profile high bootstrap (fBS70%) fraction ITBs at large radius Te/Ti effect on confinement q and density compare effects of tearing mode, fishbones, and sawteeth compare profile control techniques for SSO JET, JT-60U, ASDEX-U, DIII-D

ASIPP HT-7 Experiments of full non-inductive current drive on HT-7 X.D. Zhang, Z.W. Wu, Z.Y. Chen, X.Z. Gong, H. Wang D. Xu, Y. Huang, J. Luo, X. Gao, L. Hu, J. Zhao B.N. Wan, J. Li and HT-7 Team Institute of Plasma Physics, Chinese Academy of Science Hefei, 230031, CHINA E-mail: xdzhang@ipp.ac.cn 20th IAEA Fusion Energy Conference, 1-6 November, 2004, Vilamoura, Portugal

ASIPP HT-7 Abstract Steady-state operation is a main goal, three types of experiment are used to study long pulse discharge, steady-state operation and full non-inductive current drive on HT-7. The results show that the plasma current in the full non-inductive current drive case is instable due to no compensation of OH heating field or self-induction loop voltage, this instability of plasma current will increase the interaction of plasma with limiter and first surface and bring impurity. All discharges of full non-inductive current drive are terminated because of impurity spurting. To adjust the LHW power for control the loop voltage during long pulse discharge is the most effective method for steady-state operation on HT-7.

ASIPP HT-7 Long pulse operations on HT-7 HT-7 Superconducting Tokamak R=1.22m a=0.27m BTmax=2.2T Ipmax=250KA ne=1.0~5.0x1019m-3 Temax = 4 KeV Timax= 1.5 KeV Bottom, top and high field side toroidal limiters LHW system Multi-junction grill type, 3 rows and 4x4 columns of waveguides, Nll=1.25~3.45, fLHW=2.45GHz, PLHWmax=1.2MW Parameters for long pulse operation IP=50~60KA BT=1.8~2.0T neo=1.0x1019m-3 Te=0.5KeV PLHW =100~400KW fLHW=2.45GHz Nll=2.35

ASIPP HT-7 Long pulse operations on HT-7 Three types of long pulse operation on HT-7 tokamak The first type:long pulse discharge Plasma current droved by LHW + a fraction of OH current The second type:steady-state operation Plasma current droved by LHW + to control VL~ 0 The third type:full non-inductive current drive Plasma current droved by LHW + without OH heating field

ASIPP HT-7 Type I: Long pulse discharge Plasma current droved by LHW + a fraction of OH current A little of loop voltage supplies fraction plasma current in high performance long pulse discharge. Because of the limit of volt-second, the discharge will be terminated when the magnetic flux in iron core saturate. In this case, the pulse length is limited, so which cannot be called as steady state operation. The effect of OH heating field determines the operation state in long pulse discharge.

ASIPP HT-7 Type II: Steady state operation Plasma current droved by LHW + to control VL~ 0 It is difficult to keep VL close to zero with constant PLHW. In a high-performance tokamak for steady-state operation, a turbulence of plasma or LHW system is not unavoidable. Steady-state operation need to adjust PLHWduring discharge. A feedback control system of PLHW based on DEF signal (volt-second) is developed on HT-7, which will be used to reduce the compensation of OH heating field. The OH heating field only in a short time supplies some compensation, after the PLHW is adjusted and which can sustain the plasma current, the OH heating field will return to the initial value.

ASIPP HT-7 Type II: Steady state operation A degraded driving effect due to small density fluctuation can be compensated by OH heating field and increase PLHW. Shot: 71349 shot: 71513

ASIPP HT-7 Type II: Steady state operation The adjust value cannot be large, to the larger turbulence which is also powerless and the discharge will be terminated quickly. Shot: 71349 shot: 71513

ASIPP HT-7 Type III: Full non-inductive current drive Plasma current droved by LHW + without OH heating field “Genuine” non-inductive current drive There are two phases in this case, normally the current droved by LHW is larger than the plasma current. Phase I:negative VP, reverse compensating plasma current supplied by OH heating field to keep a constant IP. Phase II:“genuine” non-inductive current drive, VP ~ 0, IOH ~ 0, saturated magnetic flux, no multi and self-induction.

ASIPP HT-7 Type III: Full non-inductive current drive From phase I to II, the IP increase quickly in a short time (~4s) due to without multi and self-induction, or reverse compensating plasma current. The HX profile shows a off-axis deposition of LHW power in phase I and on-axis deposition in phase II on HT-7.

ASIPP HT-7 Type III: Full non-inductive current drive in “genuine” non-inductive current phase without OH heating field and self-induction loop voltage fluctuation of plasma parameters and LHW power instability of plasma current and profile interaction of plasma with limiter and first wall bring impurity or plasma density rise unfavorable for current drive

ASIPP HT-7 Type III: Full non-inductive current drive The impurity signal of CV shows that the CV radiation layer is consistent with the deposition region of LHW power and the C impurity will accumulate gradually in phase II on HT-7 (shot: 61576). 4s 18s 7x10-3 1.7x10-2 38s 51s 2.2x10-2 2.8x10-1

ASIPP HT-7 Type III: Full non-inductive current drive Non-inductive current drive without OH heating field constant IOH without OH heating field self-induction VL can retard the change of plasma current Actually which supplies a fraction of compensating current shot: 72245 shot: 70208

ASIPP HT-7 Conclusion On HT-7 the LHW power can be adjusted by means of feedback control system according to the change of DEF signal (Volt-Second) during discharge. Because of a small adjusting value, that is powerless for a larger fluctuation.The fluctuations on HT-7 are only impurity and plasma density in steady-state operation. The experiments of constant IOH show that the self-induction loop voltage cans also stabilize a larger fluctuation and retard a sudden change of plasma current in short time. To adjust the LHW power for control the loop voltage during long pulse discharge is the most effective method for steady-state operation on HT-7.

ASIPP HT-7 Discussion The “genuine” non-inductive current drive is instable due to without multi and self-induction. A fraction of compensating current in short time for steady-state operation is needed, whether the compensating fraction is supplied by OH heating field, or self-induction loop voltage. The OH heating field should be allowed to supply some compensating plasma current and keep the stability of discharge when a small plasma fluctuation appears during discharge, which will return to the initial value after fluctuation. “Full non-inductive current drive” in full space of time and “inductive one” in local space of time. The final goal of steady-state operation is how to sustain a stable discharge with high performances in long time and which will be suitable for operation mode of ITER.

Introduction of 6 th Steady State Operation ITPA Topical Group Meeting X.D. ZHANG