Overview of HL-2A Experiment Results, OV/4-1 Overview of HL-2A Experiment Results SouthWestern Institute of Physics, Chengdu, China Qingwei YANG for HL-2A Team 21 th IAEA Fusion Energy Conference, Oct. 16~22, 2006, 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, German Association Euratom-CEA, CEN Cadarache, France GA, San Diego, USA NIFS, Toki, Japan JAEA, Naka, Japan Kurchatov Institute, Russia

Overview of HL-2A Experiment Results, OV/4-1 Outline Introduction Operation regime Physics studies Summary and future plan

Overview of HL-2A Experiment Results, OV/4-1 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: B T :2.8 T2.7 T I P :480 kA400 kA Duration:3.0 s Plasma density:6.0 x m -3 Electron temp.:> 2.0 keV Ion temperature:> 800 eV Fuelling sys.: GP, SMBI, PI Heating sys.: ECRH, LHCD, NBI

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

Overview of HL-2A Experiment Results, OV/4-1 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 /q a ne·R/BTne·R/BT Disruption Greenwald limit SMBI Disruption free

Overview of HL-2A Experiment Results, OV/4-1 Outline Introduction Operation regime Physics studiesPhysics studies Summary and future plan

Overview of HL-2A Experiment Results, OV/4-1 Liquid nitrogen temperature SMBI   Supersonic molecular beam injection (SMBI) system with gas pressure of 0.2~3.0 MPa and LN temperature   A cluster contains about 250 hydrogen atoms (in average) at pressure of 1.0 MPa in this measurements   The cold molecular beam (LN temperature) 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. P 0, bar S RS, a.u. S RS ~P centeredge Room Temp. LN Temp. S RS : intensity of Rayleigh scattering

Overview of HL-2A Experiment Results, OV/4-1 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 ( ~1×10 19 m -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). Amplitude Phase

Overview of HL-2A Experiment Results, OV/4-1 Particle transport analysis with modulated MBI   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.   Formula used:   The particle diffusion coefficient on the Ohmic discharge is about 0.5 ~ 1.5m 2 /s at r/a = 0.6 ~   It is about 1/4 of the electron heat diffusivity. D(m 2 /t) r (cm)

Overview of HL-2A Experiment Results, OV/4-1 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:

Overview of HL-2A Experiment Results, OV/4-1 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),   L.W.Yan, et al., this conf., EX/P4-35.

Overview of HL-2A Experiment Results, OV/4-1 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 X.T.Ding, et al., Chin. Phys. Lett. Vol.23 (2006), T e /T i ~ 1 T e /T i ~ 1.5   χ e in plasma peripheral decreases after PI   Evidence of confinement time dependence of T e /T i is observed

Overview of HL-2A Experiment Results, OV/4-1   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 m 2 /s, V: 1 ~10 m/s at 0.2 < r/a < 0.8 Investigation of impurity transport with LBO Z.Y.Cui, Y.Huang, P.Sun, et al., Chin. Phys. Lett. Vol.23 (2006), 2143.

Overview of HL-2A Experiment Results, OV/4-1   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 dI P0 /S~t q /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. Statistic analysis of disruption J P0, MA/m Δt/S, ms/m 2 HL-2A

Overview of HL-2A Experiment Results, OV/4-1   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 Sawtooth behaviours in ECRH experiment Yi Liu, et al., this conf., EX/P8-13

Overview of HL-2A Experiment Results, OV/4-1   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. Coupling between m = 1 and m = 2 oscillation Snake m = 1 m = 2 Mirnov SX04 SX07 SX t, ms SX13 SX15 SX13SX15 Freq. kHz 10 0

Overview of HL-2A Experiment Results, OV/4-1   In experiment, the phenomenon similar to the partially detached divertor regime is observed with n e = 1.5×10 19 m -3 in main plasma.   Numerical analysis of HL-2A divertor discharges is done using SOLPS 5.0 code. It is the linear regime at n e ≤ 0.5×10 19 m -3 ; Detached phenomenon appears at 2×10 19 m -3 ≤ n e ≤ 3×10 19 m -3   The reason for the easy detachment may be the long divertor legs and thin divertor throats. Detached divertor is observed n e = 0.5×10 19 m -3 n e = 2.5×10 19 m -3 n e = 3.0×10 19 m -3

Overview of HL-2A Experiment Results, OV/4-1 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 0.5~1.5m 2 /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 m 2 /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.

Overview of HL-2A Experiment Results, OV/4-1 Summary and future plan (2) H - mode operation and physics:H - mode operation and physics: Realizing the H-mode discharge by ECRHRealizing the H-mode discharge by ECRH Pedestal physics studiesPedestal physics studies High Beta operationHigh Beta operation ConfinementConfinement Impurity, particle transport, thermal transportImpurity, particle transport, thermal transport Synergy of ECCD & LHCD: using 2 MW ECCD and 1MW LHCDSynergy of ECCD & LHCD: using 2 MW ECCD and 1MW LHCD Disruption control:Disruption control: Disruption prediction, Disruption mitigation by SMBIDisruption prediction, Disruption mitigation by SMBI Zonal flows: studies of low-frequency ZFsZonal flows: studies of low-frequency ZFs MHD instabilities:MHD instabilities: Seed island/sawteeth controlSeed island/sawteeth control Mode coupling studiesMode coupling studies Investigation of ELMs in H-mode dischargesInvestigation of ELMs in H-mode discharges Divertor physicsDivertor physics

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