J. Plasma Fusion Res. SERIES, Vol. 9 (2010)

Investigations of ICRF heating scenarios on EAST plasma
X.J. Zhang, Y.P. Zhao, C.Q. Qin, J.P. Qian

Institute of Plasma Physics, Chinese Academy of Sciences(Received: 30 October 2009 / Accepted: 28 April 2010)

For designing scenarios with optimal ICRF performances in EAST tokamak plasma, the fast wave propagation andabsorption should be first investigated. Here several possible Ion Cyclotron Resonance Heating (ICRH) scenarios havebeen explored are minority heating of hydrogen in a deuterium plasma and mode conversion heating of 3He in a deuterium
plasma. The TORIC code has been used to simulate the heating. TORIC solves the finite Larmor radius wave equations in
the ion cyclotron frequency range in an arbitrary axisymmetric toroidal geometry. The fast wave propagation/absorption
characteristics, power partitions among plasma species are analyzed.
Keywords: Minority Heating, Mode Conversion, EAST

radius current and the ion and electron FLR currents,respectively. The resulting wave equations describe
damping by the ions at the fundamental ion cyclotron
frequency and its first harmonic and Cerenkov dampingby electrons. The wave equations solved by TORIC arederived from Vlasov equation by expanding theelectro-magnetic fields in Fourier modes in the toroidaland poloidal angles. While for the FW an expansion tosecond order in the Larmor radius is adequate, large
Larmor radius effects are taken into account to describe
Ion Bernstein Wave (IBW) [5]. The TORIC code has
been improved by the parallelization of solver [6].
TORIC has been coupled to the 2D Fokker-Planckcode for ions, SSFPQL [7-9]. It solves the steady-state
surface averaged quasi-linear Fokker-Planck equation forions heated at the fundamental and the first cyclotron
harmonics by using the output of TORIC to build thesurface averaged quasi-linear diffusion coefficient. ThH
code provides information on the radial profiles of thesuprathermal populations generated by ion cyclotron
heating, and on the collisional redistribution between
these tails and the background ions and electrons. Theseare very crucial for the quasi-linear analysis.

1. Introduction

EAST tokamak [1] is to perform advanced tokamak
research in a high performance regime and to explore
methods for achieving steady-state operation for a
tokamak fusion reactor. Heating and current driving using
fast wave in the ion cyclotron range of frequencies is oneof the main features in EAST tokamak. Different ICR
heating modes are required to meet the requirements forthe initial operation, including minority and second
harmonic heating and mode conversion heating. Possible
species mixed include dominantly D with H minority or
D plasmas with 3He minority for initial operation. In
order to contribute to the development and understandingof the ICRH in EAST, we have been analyzing various
options by using the TORIC full wave code. In thismodeling study here, two physical scenarios are
considered: (a) Fast Wave (FW) minority heating with H
in D plasma at 36 MHz; (b) FW mode conversion
electron heating with 3He in D plasma (5%H fixed) at 32
MHz. An analysis of the numerical results is alsopresented in this paper.

2. The TORIC code

TORIC [2㧘3㧘4] solves the Maxwell wave equation
given by*uu EZ2 § *3. Results of numerical modeling

We present an analysis of possible two ICRF heating
scenarios for EAST. The results are for a single toroidal
mode number, nM 12 for 36MHz and nM 15 for32MHz.
Thedensity and temperature are assumed to haveprofiles inside the separatrix:

4Si·E
JP  JA ¸2 ¨Zc ©
¹
Where J P is the plasma current and J A the antenna

current. In the Finite Larmor Radius (FLR)
approximation, the plasma current can be approximatedbyJpJ

Where J00 ¦ Ji  Je2,J22Ions
2iand J e

denote the zero Larmor

2nene 0  nsep 1  r aTD

TD 0  TD sep 1  r a nsep ,2

 TD sepauthor’s e-mail: xjzhang@ipp.ac.cn

610©2010 by The Japan Society of Plasma
Science and Nuclear Fusion Research

X.J. Zhang et al., Investigations of ICRF Heating Scenarios on EAST Plasma(Di or e)

3.1 H/D Heating Scenarios

In this section, we mainly discuss the results of ICRF
minority ion heating by using the TORIC code. The fast
wave propagation and absorption characteristics, andpower partitions among electrons and ions areinvestigated.
We have used the parameters of MHD equilibrium
at t=3.6s in the shot of 9088 of EAST during 2008
campaign. The main parameters of MHD equilibrium arecalculated by using EFIT code with data fromexperiments. The results are for the toroidal mode number,nM 12 and 36 MHz

Fig.2 the radial power deposition profile: the meaning ofblue line is power to H Fundamental harmonic. The
meaning of green line is power to D second harmonic.
The meaning of pink line is power to electrons. The
meaning of red line is power to D Fundamental harmonic.
The meaning of sky blue line is power to H secondharmonic.

The main plasma parameters for study are asfollows:㧘   nsep 5 u 1012 cm3 㧘ne03 u1013 cm 3Te 02keV 㧘 Ti0 2keV㧘Tesep

0.2keV 㧘 Tisep

IP500kA, BT

0.2keV 㧘 f36MHz 2 .5 T

Fig.3 the electron power deposition profiles: the meaningof red line is total power to electrons. The meaning ofgreen line is power to electrons due to fast wave. Themeaning of blue line is power to electrons due to IBW.

Fig.1 the power fraction coupled to various species vs theminority concentration: the meaning of Fund is power toFundmental harmonic. The meaning of Harm is power tosecond harmonis. The meaning of Electrons is power toelectrons,

Fig.2 and fig.3 display the corresponding power
deposition profile of the plasma species. The location of
fundamental resonance is at 7.365 cm on the low fieldside and ion-ion resonance is at 5.050cm on the high fieldside. Over 90% of total absorbed power is going toplasma ions through the fundamental cyclotron resonanceof H and the second harmonic resonance of D with
PH=89.95% and PD= 6.58%. The rest is absorbed byelectrons with Pe =3.47% through Electron Landau
Damping (ELD) and Transit-Time Magnetic Pamping(TTMP) or by mode-converted IBW. The fast wave
excited from the low field side antenna propagates
towards the magnetic axis. The waves encounter first theIn fig.1, the power fraction coupled to various
species are plotted vs the H concentration at a fixed valueof the toroidal mode number 12. The peak is centered ona minority concentration of 9%.

611

X.J. Zhang et al., Investigations of ICRF Heating Scenarios on EAST Plasma

preliminary calculations show that the fractions of powertransfer to electron increase from 44.32% to 62.32%
through increasing the ICRH power from 2MW to 5MW.
The electron absorptions also increase when increasing
the electron temperature.

H fundamental resonance and then the ion-ion
evanescence layer, bounded by ion-ion resonance towards
the high field side and by the cutoff towards the low fieldside. The rf power not absorbed neither by ion at
cyclotron layer nor by the electrons is partially reflected
and transmitted at ion-ion evanescence layer, and mode
converted to shorter waves.

3.2 3He/D Heating Scenarios

The main parameters for the study in this section are asfollows.

ne01u1014 cm 3 㧘Te 02keV 㧘 Ti0 2keV㧘Tesep

0.2keV 㧘 Tisep

nsep

1u 1013 cm3 㧘0.2keV 㧘 f32MHz  Here the TORIC uses simple analytic formulae forthe description of equilibrium [4] with I P 750kA
and BT 3.5T

Fig.4 Fraction of power to bulk ions and electrons vsthe minority concentration

Fig.6 RF power distribution in D (3He-H) plasmaFig.5 the effective temperature of the tail for different H
concentrations
The quasi-linear calculations were performed withTORIC-SSQLFP package. The relevant plot is shown infig.4 where the fraction of power on the bulk ions andelectrons is shown vs the H concentration. No more than
65% of the coupled power can be transferred to the bulkions. Increase the H concentration decrease the powertransferred to bulk electrons. This is confirmed by thedetails of quasi-linear calculations, as shown in fig.5. Dueto the high effective tail temperatures, most of absorbed
power is thermalized on the electrons. Further612

For a given frequency and magnetic field, the location of
the mode conversion layer and electron power deposition
can be varied by changing the 3He concentration. Fig. 6
shows the power distribution for the same parameters
above. In D (3He-H) scenarios, there is a clear transition
to mode conversion dominant regimes around the 3He ofminority concentration greater than 10%. As 3He
increases, the fraction of rf power which can reach 3He
cyclotron resonance layer decreases rapidly.

X.J. Zhang et al., Investigations of ICRF Heating Scenarios on EAST Plasma

conversion heating regime, FW are mode converted toshort wavelength waves. These waves damp strongly onelectrons, giving rise to electron heating on the shortertime scale of electron-electron collisions. As is shown infig. 8, three waves—ICW, IBW and FW, are resolved at
the mode conversion layer. IBW go the high field side.
ICWs travel towards the low field side above and below
the midplane.

4. Conclusions
The TORIC code has been used to simulate theheating. The fast wave propagation and absorption
characteristics, power partitions among plasma species
are analyzed. The minority heating in EAST tokamak isinvestigated by using TORIC package which takes into
account the EAST magnetic field structure. ICRH power
absorbed by minority ions is maximized for H
concentration around 9%. Quasi-linear calculations showthat no more than 65% of the coupled power can betransferred to the bulk ions. Increase the H concentration
decrease the power transferred to bulk electrons. Theelectron absorptions also increase when increasing theelectron temperature.Increase in effective temperature
decreases the fractions of power transferred to the bulkions. EAST reference scenarios with 32 MHz at B=3.5 T
shows a clear transition to mode conversion dominant
regimes in D (3He-H) scenarios. In mode conversion
regime, the electron absorbed almost all of the absorbed
power.

Fig.7 The radial power deposition profiles for the mode
conversion case with mixture of D:3He:H (29:33:5).

5. References[1] Jiangang Li, 1st EAST IAC Meeting, 2003
[2] M.Brambilla Nucl. Fusion 34 (1994) 1121
[3] M.Brambilla Plasma phys. Control.Fusion 31(1989) 723[4] M. Brambilla Plasma phys. Control.Fusion 41 (1999) 1[5] M.Brambilla 27th EPS Conf. on Controlled Fusion andPlasma Physics 2000
[6] J.C.Wright, P.D.Bonoli, et al. Comp.Phys.Comm. 164(2004)
330[7] M.Brambilla and R.Bilato Nuclear. Fusion 46(2006)S387[8] M.Brambilla, R.Bilato,J.C.Wright,P.Bonoli 33rd EPS
Conference on Plasma Phys. 2006
[9] A.Cardinali,B.Esposito,F.Rimini,M.Brambilla,F.Crisanti,etal. 33rd EPS Conference on Plasma Phys. 2006

Fig. 8 The contour plot of fast wave field .Converged
TORIC simulation of the mode conversion case with
mixture of D-3He-H.
According to the simulations for 33% 3He with 5% H
in D plasma in fig.7, the power partition among theabsorbing species was as follows: the absorbed rf power
due to FW and mode conversion electron heating is90.3%. The FW power is absorbed via fundamental 3He
cyclotron damping is 4.1%. The remaining 5.6% of thepower is absorbed via fundamental Deuterium cyclotron
damping on the tokamak high field side. In mode613