The absorption coefficient of a magnetized plasma for cyclotron radiation

Abstract

The interaction of cyclotron radiation with a relativistic Maxwellian plasma has been re-examined with the aim of developing a computational method which will be useful for the range of parameters of interest in tokamak studies. A suitable method and the resulting computer code are briefly sketched. A sampling of results is presented and compared with previously published approximate results. A discrepancy in the ordinary-wave interaction at 90° propagation is pointed out. A simple model is discussed which permits easy extension of the computational method to include runaway electrons, and illustrative results are presented.

Extraordinary mode absorption at the electron cyclotron harmonic frequencies as a tokamak electron temperature diagnostic

“…The absorption of cyclotron harmonic radiation by tenuous, weakly damping suprathermal electron components has been investigated using the OPAKE2 [13] and ECSORB [14] codes. OPAKE2 is an up-to-date version of the earlier, well known, OPAKE code which computes the opacity of high temperature and streaming Maxwellian distributions.…”

Improved calculation of synchrotron radiation losses in realistic tokamak plasmas

“…Such values have been obtained in recent JT-60U high performance discharges near steady state [14]. The temperature profile is described using the following radial dependence: (11) where α T and β T are peaking parameters for the electron temperature profile and T ea is the edge electron temperature. For the present quantitative analysis we take a T = 8, β T = 5 and T ea = 1 keV, corresponding to a typical advanced temperature profile (very close to the one plotted in Fig.…”

“…anti-Hermitian part of the dielectric tensor, which has been proposed by Granata and Fidone [9]. This formulation avoids the standard Larmor radius expansions of Bessel functions (used, for example, by Tamor [11]) and gives very accurate values, at least in the temperature range 10-50 keV, for all frequencies. When the ray path is parallel or almost parallel to the magnetic field, the value of Bessel functions appearing in this theory becomes undefined, in which case we use asymptotic expansions giving a precision better than 10 −6 .…”

“…The electron temperature profile is modelled using the radial dependence in Eq. (11), which allows the description of a large variety of profiles. There the edge electron temperature T ea is fixed to 1 keV for our calculations.…”

Absorption around the electron cyclotron frequency in a thermal plasma of finite density

“…The absorption and the emission of electromagnetic waves in the range of the electron cyclotron frequency have recently attracted much interest [Litvak et al, 1977;Audenaerde, 1977;Freund and Wu, 1977;Fidone et al, 1978;Tamor, 1978] not only because of their importance for plasma heating [Litvak et al, 1977;Alikaev et al, 1976] and as a loss mechanism [Rosenbluth, 1970;Bekefi, 1966;Engelmann and Curatolo, 1973], but also for their potential as a diagnostic tool [Bekefi, 1966;Engelmann and Curatolo, 1973;Celata and Boyd, 1977]. Whereas the interaction of electromagnetic waves with frequencies around the harmonics of the electron cyclotron frequency to c under many conditions appearing in laboratory plasmas can be described treating thermal effects as a small correction [Au- denaerde, 1977], this is generally not the case for frequencies around the electron cyclotron frequency itself.…”