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Overview of HL-2A experiments

Overview of HL-2A experiments. HL-2A Team, presented by Qingwei YANG. S outh W estern I nstitute of P hysics, Chengdu, 610041 China. 3 rd PRC-USA Magnetic Fusion Collaboration Workshop May. 18~19 2006 Dalian, China. Introduction

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Overview of HL-2A experiments

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  1. Overview of HL-2A experiments HL-2A Team, presented by Qingwei YANG SouthWestern Institute of Physics, Chengdu, 610041 China 3rd PRC-USA Magnetic Fusion Collaboration Workshop May. 18~19 2006 Dalian, China

  2. Introduction Since the last China-USA workshop in 2004, Kunming, China. the plasma parameters of the HL-2A tokamak have been increased significantly as the improvement of the hardware of the device. The stable and reproducible discharges with divertor configuration have been obtained by the feedback control and wall conditioning. Up to now, the main plasma parameters are as follows: • Toroidal field: 2.8 T 2.7 T • Plasma current: 480 kA 400 kA • Flux: 5.0 Vs 5.0 Vs • Duration: 3.0 sec. • Plasma density: 6.0 x 1019 m-3 • Electron temp.: 1.2 keV • Ion temperature: 800 eV • Fuelling sys.： GP、SMBI、PI • Status of device. • Operation. • Recent results. • Plans in experiments.

  3. 1.5MW/50keV/2S • NBI system CXRS MSE Fuelling system 2*500Kw/68GHz/1S ECRH system ECE HCN MW reflectometer 2*500Kw/2.45GHz/1S LHCD system TS VUV Bolometer SDD 2*500Kw/68GHz/1S ECRH system Fast probes NPA • 1.5MW/50keV/2S • NBI system Other Diagnostics, … … Layout of HL-2A

  4. ECRH ECRH/ECCD heating The fundamental O-mode EC wave with the wide steering angles in poloidal and toroidal direction can modify the profiles of electron temperature and plasma current.

  5. The reproducible discharges had been obtained using feedback control. The high density discharges are achieved by gas-puffing, molecular beam injection and pellet injection. The Greenwald limit have been exceeded. Reproducible discharges Improvement of plasma current Shot:03039 Shot:03037 Shot:03038 Shot:03054 0.5 1/qa Disruption Greenwald limit 0.0 0.0 4.0 ne·R/BT Discharges on HL-2A

  6. SH: 01766 140 -81 Ip, kA Z, cm -87 -80 Z, cm -86 5 D⊥, cm D∥, cm -5 20% Imp2/Imp1-3 Imp2/IP IV/IP 0 0 T, ms 350 t/ms Sustainment of divertor configuration • The single null divertor configuration has been obtained by adjusting the multi-pole field to a suitable value. • The sustained divertor scenarios has been achieved by the reliable feedback control. Chin. Phys. Lett. Vol.21(2004) No.12 2475

  7. Wall conditioning • The siliconization was based on the chemical vapor deposition by using glow discharge cleaning (GDC) system and gas mixture of 90﹪He+10﹪SiH4. • After siliconization the impurity released and the gas recycled from the first wall were reduced obviously.The total radiated power measured by the bolometer decreased from 70% to 35%. • A local deposition of silicon during plasma discharges by silane gas puffing is also adapted. The results of the subsequent discharges show a similar effect on the plasma performance as the conventional wall conditioning by siliconization. Oral presentation on PSI in Hefei, China May 22 2006

  8. Confinement improvement after pelIet injection The advanced scenario with weak positive /negative shear of current profiles, calculated by TRANSP code using experimental data, have been achieved by the central fuelling of pellet injection (PI). The improved confinement can keep about 500 ms.

  9. r=102mm r=102mm r=163mm r=163mm r=202mm r=202mm r=238mm r=238mm χe= r2/8 tp = 0.122/ (8*0.5 x10-3) =3.6 m2/s χe = r2/8 tp = 0.122/ (8*1.5 x10-3) =1.2 m2/s Confinement improvement after pelIet injection The heat pulses propagate slower than that before pellet injection

  10. p3 37.50 p2 22.50 p1 Zonal flows • a novel design of three-step Langmuir probes (TSLPs) has been developed for ZF measurements. • Three TSLP arrays are used to identify the properties of zonal flows. They have the poloidal span of 6.5 cm and toroidal span of 80 cm. • Three dimensional GAM features are analyzed for the first time. The poloidal mode (m~0-1) and toroidal mode (n~0) of electric potential and field perturbations are simultaneously determined. Submitted to PRL

  11. Molecular beam injection Submitted to 21st IAEA Conf. Submitted to 33rd EPS Conf. • the molecular beam injection (MBI) system with gas pressure of 0.2~3.0 MPa was used. • The molecular beam penetrate into the plasma about 8cm at 0.55 MPa, and r=19cm at 3.0 MPa. • The cold molecular beam (liquid N2) could penetrate more deeply.

  12. Particle transport studies during MBI • Observation of cold pulse perturbation during MBI on HL-2A • The propagation depth of cold pulse at the two sides of plasma column during MBI is asymmetric. • The propagation depth is about ~29cm in LFS and is only about 11cm in HFS. The cold pulse propagation measured by ECE second harmonic published on PPCF, 2005

  13. Particle transport studies during MBI Profiles of the Amplitude and the phase of the heat pulse of the soft x ray measurement. published on PPCF, 2005

  14. Particle transport studies during MBI The pulsed molecular beam as a modulated source has been used. When the MBI with the gas pressure 5.5Mpa is injected into the plasma, the electron density at the different minor radius can be modulated.

  15. Particle transport studies during MBI With the higher pressure ( 6.0Mpa) and lower density, the penetration of the MB is deeper.

  16. D(m2/t) r (cm) Particle transport studies during MBI After the FFT, the amplitude and the phase profiles of the first harmonic and high harmonic can be obtained, respectively. The amplitude and the phase profiles show that the perturbation particle source injected by pulse MBI is located about 23-28 cm, where the obvious minimum phases can be observed. The maximum amplitude of the first harmonic shifts inward, indicating the presence of the inward convective component. At the second harmonic, this feature disappears and a standard diffusive pattern can be found. Therefore, we can obtained the diffusion coefficient and the convective velocity from the method. D =ω/2 (dΦ/dr)2 ω : freq. of the modulated wave Φ : phase r : minor radius

  17. Thermal transport The thermal transport database is being constructed by employed the transport codes and experimental data. • The sawteeth oscillation is used to analysis the thermal transport. • The modulated ECRH will be used as well.

  18. 300 IP, kA 0 1.0 Pimp, a.u. CIII, 97.7nm CIII, 464.7nm 0.0 5.0 ne, m-3 ×1019 0.0 5.0 PR, a.u. r =3cm r =-20cm r =-38cm 0.0 800 Te(t), eV 0 340 r, mm Last sawtooth -330 440 485 t, ms Characteristics of disruption • Two types of the disruption are observed in the experiments. • The secondary current plateau is found not to be the runaway electrons

  19. Disruption database • the disruption database of HL-2A is built up preliminarily. • Most of the plasma current quench time is in the range of 4~6 ms in the major disruptions. • The fast quench of plasma current always leads to the great loop-voltage. • the strong MHD activities are the obvious “disruption precursor”. count

  20. Disruption prediction and mitigation • The optimized network architecture is composed of 13 inputs, three hidden layer with 15, 15, 10 hidden neurons, respectively. • a new parameter, δBθ·τp, is introduced to predict disruption. It can predict more than 95% of disruption. • The disruption mitigation by using noble gas (Neon and Argon) puffing and MBI (molecular beam injection) has been demonstrated.

  21. a b d c Impurities • Aluminum and Titanium were injected into plasma using laser blow-off. • The simulations are under analysis by employing a simple transport code. Ti (22) Al (13)

  22. m=1 oscillation 0.8 0.2 Isx (a.u.) Center channel 0.32 First sawtooth crash Outer channel T (m s) 340 360 m=1 oscillation Isx (a.u.) 0.20 MBI T (m s) Crash phase The long- lived m/n=1/1 perturbationand sawteeth after molecular beam injection. Z (m) a b Z (m) c d q=1 surface (a) Instabilities • Several important central MHD activities, for example, sawtooth suppression, monster sawtooth and, persistent m/n = 1/1 oscillations, have been observed. The simulations are under analysis by employing a simple transport code. • The tearing mode has been investigated using Mirnov coils and soft X ray emissions.

  23. Divertor physics • Numerical analysis of HL-2A divertor discharges was done using two dimensional multi-fluid edge code SOLPS5.0. • The detachment characteristics are determined under the specific divertor geometry. This results in momentum losses already at low densities from the interaction of the streaming divertor plasma with this neutral cushion. Therefore, a strong deviation from the common 2-point scaling is observed if local parameters are used, similar to island divertors in stellarators. presentation on PSI in Hefei,

  24. Physics studies in plan • H-mode operation • ELMs, pedestal physics, • ITB scenarios • Transport mechanism, turbulence, … • Heating, …, configuration control. • Confinements, … • High Beta operation • NTM, RWM, … • Impurity, particle transport, … • Radiative divertor.

  25. Future plan To improve the auxilliary heating.

  26. HL-2A HL-2M Positions of HL-2A(M)

  27. Thank you for your attention

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