Status of HL-2A HL-2A Team (Presented by Longwen Yan) Southwestern Institute of Physics, Chengdu, China Presentation for IEA PD and LT activities on May 21, 2007

OUTLINE Introduction of HL-2A tokamak Auxiliary Heating & Fueling Systems Diagnostic systems Experimental progress  Results of divertor and high density experiments  Results of SMBI fueling with LN temperature  Results of GAM zonal flows  Results of the ECRH with power of 2MW  Disruption mitigation and MHD mode coupling  Conclusions Experimental Plan in 2007 Modification for HL-2A

Introduction of HL-2A Tokamak Plasma parameters of 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. B T :2.8 T2.7 T I P :480 kA430 kA Duration:3.0 s Plasma density:6.0 x m -3 Electron temperature:~5 keV Ion temperature:>1 keV Fuelling system:GP, SMBI, PI Heating sys.: ECRH, LHCD, NBI

Auxiliary Heating & Current Drive The red values are for the next phase

Four gyrotrons provide power 2MW with f = 68 GHz Transmission system consists of oversized wave-guides with diameter of 8 cm and some metallic reflectors. Microwave is launched into plasma perpendicularly to toroidal field at the LFS as an ordinary mode Antenna structure of the ECRH system on HL-2A ECRH Quasi-Optical Transmission & Antenna HL-2A tokamak Gyrotron Window of gyrotron Mode absorption Superconducting magnet Waveguide

Fuelling Systems  Gas Puffing  Multiple Pellet Injection  Molecule Beam Injection Fueling Systems

SMBI Pellet Injection 2*500kW /1s /68GHz ECRH/CD 1.5MW/55keV/ 2s/NBI system 2*500kW/1s /68GHz ECRH/CD 2*500kW /1S /2.45GHz/ LHCD system Thomson Scattering CXRS 8-Channel HCN interferometer VUV spectrometer MW reflectometer ECE Fast reciprocating probes Neutral Particle Analyzer SDD soft X ray spectrum Bolometer & Soft X ray arrays More than 30 kinds of Diagnostics developed Diagnostic Systems

OUTLINE Introduction of HL-2A Tokamak Auxiliary Heating & Fueling Systems Diagnostic systems Experimental progress  Results of divertor and high density experiments  Results of SMBI with LN temperature  Results of GAM zonal flows  Results of 2MW ECRH  Disruption mitigation and MHD mode coupling  Conclusions Experimental Plan in 2007 Modification for HL-2A

Ip=433 kA, Bt=2.7 T, n e = 6  m -3 Te=5 keV 23 divertor discharges with good reproducibility Discharge Parameter Progress

 The discharges with lower single null configuration are often conducted  The high density is obtained by direct gas-puffing, SMBI and PI fuelling  The Greenwald density limit can be exceeded with SMBI fueling /q a ne·R/BTne·R/BT Disruption Greenwald limit SMBI Disruption free Divertor and High density Experiments

 Numerical analysis of HL-2A divertor discharges is conducted with SOLPS 5.0 code, indicating the linear regime appearing at edge density n e ≤ 0.5×10 19 m -3, detached regime in 2×10 19 m -3 ≤ n e ≤ 3×10 19 m -3  Plasma detachment is easily obtained due to the long divertor legs and thin divertor throats according to the modeling.  In experiment, the phenomenon similar to the partially detached divertor regime is observed with line averaged n e = 1.5×10 19 m -3 in main plasma. Modeling for Detached Plasma n e = 0.5×10 19 m -3 n e = 2.5×10 19 m -3 n e = 3.0×10 19 m -3

Penetration depth scaling of SMBI  The penetration depth is studied by FFT analysis with modulated SMBI  The SMBI penetration depth with room temperature depends on the electron density, temperature and the pressure of working gas  Asymmetric penetration with SMBI is observed by ECE and soft X- rays in low density ( ~1×10 19 m -3 ).  The penetration depth is about 30 cm from the LFS and only about 10 cm from the HFS  The particle diffusion coefficient is about 0.5 ~ 1.5 m 2 /s at r/a = 0.6 ~ 0.75, which is about 1/4 of the electron heat diffusivity

Cluster SMBI with LN temperature  New SMBI system using gas pressure of 0.2~3.0 MPa and Liquid Nitrogen temperature  A hydrogen cluster contains about 250 atoms at pressure of 1.0 MPa measured by the intensity of Rayleigh scattering  The cold beam with LN temperature can penetrate into plasma deeply P 0, bar S RS, a.u. S RS ~P center edge Room Temp. LN Temp. S RS : intensity of Rayleigh scattering H  intensity with/without LN Temp.

Toroidal symmetry of GAM ZF  A novel design of three-step Langmuir probes is developed for ZF study.  The radial component of electric field and gradient of Er  The toroidal, poloidal and radial coherencies of electric potential can be calculated using potentials Φ1~Φ11, Φ1~Φ6, and Φ1~Φ7, respectively.  To explore the generation mechanism of the GAM ZFs, squared cross- bicoherence is calculated:  L. W. Yan, et al., Rev. Sci. Instru. 77, (2006)

3D features of GAM Zonal Flow  K. J. Zhao, et al., Phy. Rev. Lett., 96 (2006), Bicoherence of three wave coupling  Toroidal symmetry (n ~ 0) of the GAM zonal flow in a tokamak is identified for the first time  Poloidal mode number of GAMZF is m=0-1  The radial wavelength of GAMZF is cm  Nonlinear three wave coupling is identified to be a plausible physics mechanism for the generation of the GAM ZFs.  Studies of interactions between the ZFs and the ambient turbulences are in progress.

The fundamental O-mode ECRF with the wide steering angles in poloidal and toroidal directions can modify the profiles of electron temperature and current profile. T e >3 keV is measured with TS and ECE for shot 5985 High Te obtained by ECRH

Electron Fishbone Instability m=1/n=1 mode bursts

 Most quench times of plasma currents in HL-2A are 4~6 ms in the major disruptions.  A new parameter, the amplitude multiplies the period of MHD perturbation ( ), is introduced to predict disruption.  The disruption mitigation by noble gas (Neon and Ar) puffing are demonstrated, current quench time to 20 ms from 5 ms. Statistic analysis of disruptions

 A large, persistent m = 1 perturbation with snake structure is observed in sawtooth free plasma after PI (or SMBI).  The m = 1 mode is detected with 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 of m = 1 and 2 modes Snake m = 1 m = 2 Coupling region

Summary  Maximum parameters: 433kA/2.7T/6x10 19 m -3 /5keV/3s/  A penetration depth scaling of SMBI is revealed. The cluster SMBI with LNT can penetrate deeper. The particle diffusion coefficient of modulated SMBI is m 2 /s.  3-D features of GAM ZFs are determined with novel 3-step Langmuir probes for the first time. The poloidal and toroidal symmetries (m=0~1, n = 0) of the low frequency (7~9 kHz) electric potential and field are simultaneously observed.  Electron fishbone is observed with the ECRH of 2MW/68GHz  A large, persistent m = 1 perturbation with snake structure is observed after PI (or SMBI).  A new parameter of magnetic perturbation is introduced to predict the disruption. The noble gas injection successfully increase the current quench time to 20 ms from 5 ms.  The fully or partially detached divertor is easy occurrence, even if in medium density. The numerical simulation results are in agreement with experimental ones.

Confinement, transport & turbulence study in 2007 H-mode physics with ECRH (2MW) and LHCD (0.5MW) Zonal flow mechanism with GAM and near zero frequencies Thermal transport by modulated ECRH ； non- local thermal transport via ECRH and SMBI ITB with off-axis heating and SMBI Impurity transport using LBO of Ti ， Al ， Mo. Optimization of density profile by PI and MBI. Density limit using mixed fuelling technique by GP + PI or GP + PI + MBI

MHD instability, disruption & its mitigation study in 2007 MHD stabilities in low q (q < 3) discharges Seed island suppression and sawteeth control by ECCD ELM features in H-mode discharge Disruption mitigation using the MBI of argon, impurity injection by LBO Database for disruption prediction Sawtooth activities during ECRH Correlation between MHD activities and confinement Instabilities induced by energetic electrons

Boundary and divertor physics Wall conditioning using siliconization and boronization First mirror and its properties Radiative and pumped divertor Temperature and density fluctuations Detachment physics in divertor chamber

Heating and Current Drive Optimization of heating and current drive for ECRF with 1~2 MW Synergy of ECCD & LHCD NBI heating with power 1.5 MW ITB comparison among HL-2A, TEXTOR and T-10

Plasma current I p = 1.2MA Major radius R = 1.8 m Miner radius a = 0.5 m Aspect ratio R/a = 3.6 Elongation Κ = 1.6 – 1.8 Triangularity δ > 0.4 Toroidal field B T = 2.6T Flux swing ΔΦ= 10Vs Duration t d = 3 s The main parameters HL-2M TOKAMAK

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