RF simulation at ASIPP Bojiang DING Institute of Plasma Physics, Chinese Academy of Sciences Workshop on ITER Simulation, Beijing, May 15-19, 2006 ASIPP

OUTLINE LHW ICRF Synergy of LHW and ICRF/IBW Future Considerations Summary ASIPP

LHW Coupling between LHW and Plasma Ray tracing and current drive Effect of LHCD on radial electric field ASIPP

Coupling between LHW and Plasma The launched spectrum from the LHW antenna can be calculated at a given plasma condition. Effects of wave-guide phase difference and plasma condition on the power spectrum and the reflection are obtained. LHW Spectra at different 

Ray tracing and current drive With combining a ray-tracing code and a 2-D Fokker-Planck equation, we can calculate ray-trace of wave beam, power deposition, driven plasma current profile. The radial diffusion of fast electron is considered. It is only valid for the circular cross section plasma. It can be used to explain HT-7 experimental results effectively.

Ray trace of the wave beam （ N // peak =2.95)

 Power deposition and driven current vs 

B t Power deposition and driven current vs B t

T e Power deposition and driven current vs T e

A typical waveform of LHCD experiments (#46693) n e =1.5  m -3, I p =220kA, B T =2.0T,, N // peak =2.9,P LH =240kW. ASIPP

An ITB seems visible in the region around r/a ~ 0.55 Electron temperature profiles Ion temperature profiles ASIPP

Power deposition and current density profile ASIPP

a low magnetic shear is possibly formed because of the hollow current profile inside the surface of q=2 (r/a~0.8). Experiments described in early references show that a low magnetic shear inside the q=2 surface is a favorable condition to form an ITB ASIPP

Effect of LHCD on radial electric field Based on electron’s radial force equilibrium and the LHCD simulation code, the effect of LHCD on radial electric field profile is calculated. It possibly offers a tool for explaining LHCD to improve plasma confinement.

Typical waveforms of LHCD experiment with eITB

Electron temperature profiles in OH and LHCD phase

Magnetic shear decreases during the LHCD plasma Simulation results with the experimental parameters (a) power deposition profile (b)driven current profile and q profile

A notch structure in  E r is formed near the layer with strong deposition of LHW. The largest E r (LHCD) gradient locates at the position of ~10cm, which is well consistent with the ITB region indicated by the T e profile. Simulated profiles of (a) radial electric field and (b) its shear in OH and LHCD phase

ICRF Coupling between ICW and Plasma Ray-tracing code for IC waves in tokamak plasma ASIPP

Coupling between ICW and Plasma (ANT10 from Japan) The coupling of the antenna is calculated in a slab geometry. The model is three dimensional and includes the effect of connections to a transmission line. The coupling code based on the variational principle can give the self-consistent current flowing in the antenna, the field excited inside the plasma, and the antenna impedance for circular shape plasma.

Impedance versus the distance E y distribution at the plasma surface (0,  )

Ray-tracing code for IC waves in tokamak plasma Ray trace of wave beam, power deposition profile in plasma are obtained. ICRF wave propagation and deposition for a noncircular tokamak can also be studied. Plasma temperature can be modified by the ICRF heating.

Poloidal  =0.4,  =1.8,f=55MHz,B t =3.5T, Te(0)=2.0keV, Ti(0)=3.0keV,n H / n D =0.15,ne(0)=3.5x10 19 m –3, nea=9.0x10 18 m –3 Toroidal Ray tracing for EAST D(H) scenario

Power deposition profiles for EAST D(H) scenarios at different temperatures  =0.4,  =1.8,f=55MHz,B t =3.5T,n H /n D =0.15,ne(0)=5x10 19 m –3, nea=5x10 18 m –3

Synergy of LHW and ICRF/IBW Synergy of LHW and IBW (From FTU, Italy) Synergy of LHW and ICRF Synergetic effects of LHW and IBW/ICRF are preliminarily simulated for HT-7 tokamak. The electron distribution, LHW power deposition and driven current are affected by both IBW and fast wave. The work is just a kick-off, further work is under process.

Electron distribution function with (a) LHW (b) LHW+IBW

LHW power deposition Driven current profile

Profiles of LHW power deposition and driven current without fast wave Profiles of LHW power deposition and driven current with fast wave

Future Consideration We intend to develop the simulation of coupling, propagation, heating, current drive for LHW and IBW/ICW, and the synergy of LHW and IBW/ICW for EAST tokamak, even for ITER. After that, we intend to couple the plasma transport to the above code with the co-operation of other divisions and laboratories. 1.The coupling of wave and plasma in the non-circular cross section 2.The propagation and absorption of LHW in the non-circular cross section 3.Full wave code for IC waves in tokamak for circular / noncircular plasmas (Toric, from Germany) 4.Synergetic simulation of LHW and IBW/ICRF 5.Combination of Transport and heating/drive simulation.

Summary The coupling between wave and plasma in the slab geometry is obtained, the more complicated geometries are under process. The ray tracing and current drive of LHW in circular plasma are achieved, the extension to the non-circular case is possible. The present ICRF code is based on the ray-tracing method, the full wave code (TORIC) is under development. Synergetic simulation of LHW and IBW/ICRF is underway. Combination of Transport and heating/drive simulation will be done next.

Thank you for your attention!