A. Fukuyama

T. Seki

T. Watari

Seki,  T.

Watari,  T.

Fukuyama,  A.

NIFS-Repository (National Institute for Fusion Science)

§20. Calculation of ICRF Heating Using 3-D Code (TASKlWM) Seki, T., Watari, T., Fukuyama, A. (Kyoto Univ.) The ion cyclotron range of frequency (lCRF) heating is one of heating method in LHD and good heating results are achieved in former experiments l ). To analyze the ICRF heating experiments and predict the heating conditions that higher heating efficiency is obtained in, theoretical research is also important. The wave-particle interaction in magnetically confined plasma is complex and various analyzing methods are used. The full wave calculation, which solves the wave equation as a whole, is one of such methods and can predict the special profile of the wave fields and the power depositions, and so on. The full wave calculation in a helical revice was difficult since a large quantity of computer memory and enormous calculation time are required to inclure three-dimensional helical configuration. In the former calculation, the simplified helical magnetic configuration was employed and it was difficult to realize the actual configuration of the resonance and cutoff layers. However, remarkable progress of recent computer technology mare possible to cb the three-dimensional helical calculations. The 3-D full wave core (TASKIWM) was reveloped by Vcbvin and Fukuyama2). The wave equation is solved using the expansion consirering the finite Larmor radius effect. Fast wave and more-conversion are rescribed. The plasma configuration is given by using the MHD equilibrium core, VMEC. Simple antenna configuration can be includxl. It is assumed that calculation region is surrounOOd by the perfectly conducting wall. There is a vacuum region between the wall and the plasma surface. Figure 1 shows the power reposition profile of hydrogen ion in the poloidal plasma cross section at the four different toroidal angles. In this calculation, electron rensity is lxl0l9m-3 and temperature is 1.5keV and the helium plasma with 10% of hydrogen is assumed The number of more in radial, poloidal and toroidal directions is 100, 16 and 4, respectively. Absorbed power extends to the poloidal direction in the same flux surface, not concentrating near the ion cyclotron resonance layer. Figure 2 shows the hydrogen-absorbed power as changing the wave frequency. The magnetic field strength is fixed to be 2.75T. Then, the position of ion cyclotron resonance layer is changed by the wave frequency. The resonance layer is located at the plasma periphery in 31.8MHz and moves to the insire of plasma with frequency increase. The resonance layer is located at the magnetic axis in 41.8MHz. The absorbed power by the hydrogen is very small when the ion cyclotron layer is located at the plasma edge. It increases gradually as the resonance layer approaches to the plasma core region. Almost same feature is obtained also in the experiments3). The calculations using higher numbers of mores are necessary for deeper consideration. cp=90 \ \ Fig.l. Power deposition profile of hydrogen ion in the poloidal plasma cross section at the four different toroidal angles. The ion cyclotron resonance layers are also shown. 40 --- - - ------- ---,---- - T - ----,---,......, .~ § 30 -.ci '-C'tI ~ '-! 20 r Q) I -e I ----e -·-He ·····H &1 10 1-~ I plasma edge i ! + i • 1 • ! I .• : !: !. magnetic axis . .. 1 ; .' ! ill' ! : ~ o ,- - • : :1 \-. ... JA! . . ..... ~·I ~~30 32 34 36 38 40 42 frequency [MHz] Fig.2. Dependence of power absorption by hydrogen ion on the wave frequency, i.e., the position of the ion cyclotron resonance layer. The resonance layer is located at the plasma edge in lower frequency and moves to the inside of plasma with the increase of frequency. References 1) Seki, T. et al.: 14th Top. Conf., AlP 595(2001)67. 2) Vdovin, V.L. et al.: NIFS-469(1996). 3) Saito, K.: Nucl. Fusion 41(2001)1021. 133 

Calculation of ICRF Heating Using 3-D Code (TASK/WM)

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