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Overview of HL-2A Experiment Results

Overview of HL-2A Experiment Results. Qingwei YANG for HL-2A Team. S outh W estern I nstitute of P hysics, Chengdu, China. Cooperated with: University of Science and Technology of China, Hefei, China Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China

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Overview of HL-2A Experiment Results

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  1. Overview of HL-2A Experiment Results Qingwei YANG for HL-2A Team SouthWestern Institute of Physics, Chengdu, China Cooperated with: University of Science and Technology of China, Hefei, China Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China Institute of Physics, Chinese Academy of Sciences, Beijing, China Tsinghua University, Beijing, China MPI für Plasmaphysik, Association Euratom, GermanAssociation Euratom-CEA, CEN Cadarache, France GA, San Diego, USA NIFS, Toki, Japan JAEA, Naka, Japan Kurchatov Institute, Russia 21th IAEA Fusion Energy Conference, Oct. 16~22, 2006, Chengdu, China

  2. Outline • Introduction • Operation regime • Physics studies • Summary and future plan

  3. Introduction Since the last IAEA Fusion Energy Conference in 2004, the plasma parameters of the HL-2A tokamak have been increased significantly with the improvement of the hardware. The stable and reproducible discharges with divertor configuration have been obtained by reliable feedback control and wall conditioning techniques. Up to now, the main plasma parameters are as follows: • BT: 2.8 T 2.7 T • IP: 480 kA 400 kA • Duration: 3.0 s • Plasma density: 6.0 x 1019 m-3 • Electron temp.: > 2.0 keV • Ion temperature: > 800 eV • Fuelling sys.: GP, SMBI, PI • Heating sys.: ECRH, LHCD, NBI

  4. 1.5MW/50keV/2sNBI system SMBIPellet Injection, 2*500kW /1s /68GHz ECRH/ECCD 2*500kW /1S /2.45GHz LHCD system 2*500kW/1s /68GHz ECRH/ECCD ECE CXRS 8-Channel HCN interferometer MW reflectometer Thomson Scattering VUV spectrometer Bolometer & Soft X ray arrays SDD soft X ray spectrum Fast scan probes Neutral Particle Analyzer Other Diagnostics, … …

  5. 0.5 SMBI Disruption 1/qa Disruption free Greenwald limit 0.0 0.0 5.0 ne·R/BT Operation regime • The sustained divertor discharges are achieved by reliable feedback control. The low single null divertor is the usually used configuration on HL-2A. • The high density discharges are obtained by gas-puffing, SMBI and PI. • The Greenwald limit can be exceeded.

  6. Outline • Introduction • Operation regime • Physics studies • Summary and future plan

  7. SRS~P01.4 SRS, a.u. P0, bar Liquid nitrogen temperature SMBI • Supersonic molecular beam injection (SMBI) system with gas pressure of 0.2~3.0 MPa and LNtemperature • A cluster contains about 250 hydrogen atoms (in average) at pressure of 1.0 MPa in this measurements • The cold molecular beam (LNtemperature) can penetrate into plasma deeply • The MBI with clusters may be of benefit for deeper fuelling • L.H.Yao, et al., this conf., EX/P3-21. SRS: intensity of Rayleigh scattering Room Temp.LN Temp. center edge

  8. Amplitude Phase Penetration depth scaling of SMBI • The penetration depth is studied with FFT analysis of modulated injection and tangential H-alpha array to detect the penetration depth. • The penetration depth (working gas is at room temperature) is dependent on the plasma parameters and pressure of working gas. • Asymmetric penetration using SMBI is observed in low density ( ~1×1019m-3) by ECE and soft X- ray.The penetration depth is about 30 cm from the low field side (LFS) and only about 10 cm from the high field side (HFS).

  9. D(m2/t) r (cm) Particle transport analysis with modulated MBI • Formula used: • The particle diffusion coefficient on the Ohmic discharge is about 0.5 ~ 1.5m2/s at r/a = 0.6 ~ 0.75. • It is about 1/4 of the electron heat diffusivity. • Particle transport is studied with modulated SMBI and microwave reflectometer. • After the FFT, the amplitude and the phase profiles of the first harmonic and high harmonics can be obtained.

  10. Study of toroidal symmetry of GAM ZFs (1) • A novel design of three-step Langmuir probes is developed for ZF detection. • The radial component of electric field and gradient of Er • The poloidal and toroidal coherencies of electric potential can be calculated using Φ1~Φ6, and Φ1~Φ11, respectively. • To explore the generation mechanism of the GAM ZFs, squared cross-bicoherence is calculated:

  11. Study of toroidal symmetry of GAM ZFs (2) • Toroidal symmetry (n ~ 0) of the GAM zonal flow in a tokamak is identified for the first time. • 3-D spatial features of the GAM ZFs are analyzed, simultaneously. • Nonlinear three wave coupling is identified to be a plausible physical mechanism for the generation of the GAM ZFs. • Studies of interactions between the ZFs and the ambient turbulences are in progress. • K.J.Zhao, et al., Physical Review Letters, 96 (2006), 255004 • L.W.Yan,et al., this conf., EX/P4-35.

  12. Confinement improvement after pelIet injection • The q profile is reconstructed with TRANSP code using experimental data The weak magnetic shear is achieved after PI • The improved confinement sustains about 500 ms Te/Ti ~ 1 Te/Ti ~ 1.5 • χe in plasma peripheral decreases after PI • Evidence of confinement time dependence of Te/Ti is observed • X.T.Ding, et al., Chin. Phys. Lett. Vol.23 (2006), 2502.

  13. Investigation of impurity transport with LBO • Al and Ti are injected into plasma using laser blow-off. • the transport of impurity in plasma center is slower than that in the outer region. • The transient asymmetric profile, inward transport and outward diffusion are observed using tomography of the soft X ray radiation. • D: 0.5 ~ 1.0 m2/s, V: 1 ~10m/s at 0.2 < r/a < 0.8 • Z.Y.Cui, Y.Huang, P.Sun, et al., Chin. Phys. Lett. Vol.23 (2006), 2143.

  14. 1000 Δt/S, ms/m2 0.1 0.1 JP0, MA/m2 10 Statistic analysis of disruption • Most of the plasma current quench time is 4~6 ms in the major disruptions. • The induced loop-voltage is proportional to the current quench rate. • The disruption regime in the dIP0/S~tq/S plane is identified. • A new parameter, , is introduced to predict disruption. The physical meaning of this parameter is the amplitude multiplies the period of MHD perturbation. • The disruption mitigation by noble gas (Neon and Argon) puffing are demonstrated. HL-2A

  15. Sawtooth behaviours in ECRH experiment • The saturated sawtooth and strong m = 1 precursor is found during on-axis ECRH. The period of sawtooth decreases during on-axis ECRH discharges • The heat transport increases in on-axis ECRH discharges • Yi Liu, et al.,this conf., EX/P8-13

  16. SX04 Snake SX07 SX10 SX13 m = 1 SX15 Mirnov m = 2 SX13 SX15 1650 1850 t, ms Coupling between m = 1 and m = 2 oscillation • A large, persistent m = 1 perturbation of snake structure is observed in sawtooth free plasma after PI (or SMBI). • This m = 1 mode is detected by soft X ray arrays, but not detected by Mirnov coils. • An m = 2 magnetic perturbation with the same frequency is observed during the decay of m = 1 mode. Freq. kHz 10 0

  17. ne = 0.5×1019m-3 ne = 2.5×1019m-3 ne = 3.0×1019m-3 Detached divertor is observed • In experiment, the phenomenon similar to the partially detached divertor regime is observed with ne = 1.5×1019m-3 in main plasma. • Numerical analysis of HL-2A divertor discharges is done using SOLPS 5.0 code. It is the linear regime at ne ≤ 0.5×1019m-3;Detached phenomenon appears at 2×1019m-3≤ ne≤ 3×1019m-3 • The reason for the easy detachment may be the long divertor legs and thin divertor throats.

  18. Summary and future plan (1) • The detailed investigations of SMBI are carried out. A penetration depth scaling is revealed.The LNT SMBI can penetrate into plasma more deep.The MBI with clusters may be of benefit for deeper fuelling; The penetration depth of SMBI is much deeper in LFS than in HFS at low density discharges. • The particle diffusion coefficient is about 0.5~1.5m2/s in plasma peripheral region, using microwave reflectometer and modulated SMBI. • 3-D features of GAM ZFs are determined with novel designed 3-step Langmuir probes. The symmetries (m=0~1, n = 0) of the directly measured low frequency (7~9 kHz) electric potential and field are simultaneously observed. • The diffusion coefficient D and convection velocity V of impurity are fitted using LBO: D = 0.5~1.0 m2/s, V = 1 ~ 10 m/s. • A new parameter is introduced to predict the disruption. The noble gas injection successfully increase the current quench time from 5 ms to longer than 20 ms. • A large, persistent m = 1 perturbation of snake structure is observed in sawtooth free plasma after PI (or SMBI). An m = 2 magnetic perturbation with the same frequency is induced by the m = 1 mode. • The detached (or partially detached) divertor regime is easily occurrence, even in the intermediate density operation. The reason may be the long divertor legs and thin divertor throats. The numerical simulations are in good agreement with the experiments.

  19. Summary and future plan (2) • H - mode operation and physics: • Realizing the H-mode discharge by ECRH • Pedestal physics studies • High Beta operation • Confinement • Impurity, particle transport, thermal transport • Synergy of ECCD & LHCD: using 2 MW ECCD and 1MW LHCD • Disruption control: • Disruption prediction, Disruption mitigation by SMBI • Zonal flows:studies of low-frequency ZFs • MHD instabilities: • Seed island/sawteeth control • Mode coupling studies • Investigation of ELMs in H-mode discharges • Divertor physics

  20. Thanks for your attention

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