A. Mase

H. Hojo

K. Kawahata

T. Tokuzawa

National Institute for Fusion Science (NIFS-Repository)

Simulation Study for Technology Development to Make Reflectometer Highly Accurate Hojo, H. (Univ. Tsukuba) Mase, A. (Kyushu Univ.) Tokuzawa, T., Kawahata, K. (NIFS) For burning plasma such as ITER, electron temperature is expected to be several ten’s keV.  For such plasma, the relativistic effect of electrons becomes important in fusion researches. We study the effects of the relativistic correction of electron mass on microwave diagnostics [1-4]. The dispersion relation of ordinary (O) mode for a relativistic Maxwellian plasma is given by 2/1211 ������������������� ���peANkc,  (1) where A denotes the relativistic correction of electron mass for O-mode cutoff, and is given by, for � << 1,  ������ 251)()(302422 ����� �epdpKA ,  (2) with � = mec2/Te, � = (1+p2)1/2, p = |p|/(mec), me the electron mass, c the light speed, Te the electron temperature, and K2(�) is the modified Bessel function. In Ref.3, the relativistic correction A = (1+5/�)1/2 is proposed, which is approximately equal to eq.(2) for�������.  We see that A� 1 as Te � 0.  We show A = 1+5/2� as a function of Te in Fig.1 and it is found that 1+5/2� is in good agreement with the exact form A up to 60keV of Te.In interferometry, the phase difference in plasma and vacuum propagation is important in the density profile reconstruction, and is given by � � �� ���� 2121)1(20yyyydyNdykk ��� ,  (3) where k0 = �/c =2�/� is wave number in vacuum.  When ���� �pe, eq.(3) is approximated by  �� ����axyyccxrxrrdrArnndyArnnr ,)()()(2221 ����� , (4)where nc = �2me�0/e2 and a is a plasma–vacuum boundary. The Abel inversion equation with the relativistic mass correction of electron is given by rxrxdxdxdnArnarc ���� � ,)(222���. (5) Therefore, the reconstructed density profile of eq.(5) is taken into account of the relativistic mass correction of electron by the factor A. The relativistic correction is also important in reflectometry. Recently, LHD plasma has been achieved over ten keV of electron temperature. The example of such high temperature plasma experiment is shown in Fig.2. In this discharge, the center electron temperature is over 15 keV and the line-averaged correction factor is 1.017. Then, the interferometer signal needs to be modified by 1.7 % correction.Fig. 1. Relativistic mass correction of electron Fig. 2. Radial profile of relativistic electron mass correction at the high electron temperature plasma experiment in LHD 1) D. B. Batchelor et al., Phys. Fluids 27 (1984) 2835. 2) H. Bindslev, Plasma Phys. Control. Fusion 35 (1993) 1093.3) E. Mazzucato, Phys. Fluids B4 (1992) 3460.  4) H. Hojo et al., Plasma Fusion Res. 2 (2006) S1022. 157§8. Si ulation Study for Technology Development to Make Reflectometer Highly AccurateHojo, H. (Univ. Tsukuba),  Mase, A. (Kyushu Univ.),  Tokuzawa, T., Kawahata, K.

Simulation Study for Technology Development to Make Reflectometer Highly Accurate

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