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1 - Nuclear Sciences and Applications - IAEA

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<strong>IAEA</strong>-CN-50/E-IV-ll 773<br />

gests that in very high temperature, large plasmas, complete first pass absorption at<br />

large frequency downshifts can be achieved.<br />

5. CONCLUSIONS<br />

We have investigated the propagation <strong>and</strong> absorption of electromagnetic waves<br />

in a weakly relativistic Maxwellian plasma in the presence of a non-drifting or current<br />

carrying superthermal tail, with the main objective of clarifying whether the frequency<br />

requirements of the SECH plasma heating can be reduced. The results<br />

obtained indicate that in the range of bulk electron temperatures T = 1-4 keV, ><br />

X-waves whose frequency is significantly lower than the central SECH frequency,<br />

w < 2coc(0)/(l + A" 1 ), produce good power deposition profiles in large plasmas.<br />

In small <strong>and</strong> medium size plasmas (koa < 10 3 ), moderate frequency downshifts of<br />

the X- or O-mode are more effective in heating the central plasma region. Both the<br />

non-drifting <strong>and</strong> current carrying (at Nf < 0) superthermal tails substantially<br />

improve the wave absorption efficiency at downshifted frequencies. Higher electron<br />

temperatures allow the use of waves with larger frequency downshifts in medium size<br />

plasmas as well as an effective optimization of the power deposition.<br />

REFERENCES<br />

[1] MAZZUCATO, E., FIDONE, I., GIRUZZI, G., KRIVENSKI, V., Electron cyclotron heating<br />

at down-shifted frequencies in existing tokamak devices, Nucl. Fusion 26 (1986) 3-9.<br />

[2] FIDONE, I., GIRUZZI, G., MAZZUCATO, E., Electron cyclotron heating of a tokamak reactor<br />

at downshifted frequencies, Phys. Fluids 28 5 (1985) 1224.<br />

[3] BORNATICI, M., RUFFINA, U., "Electron cyclotron absorption at downshifted frequencies in<br />

presence of a superthermal tail", Controlled Fusion <strong>and</strong> Plasma Physics (Proc. 14th Eur. Conf.<br />

Madrid, 1987), Vol. HD, Part II, European Physical Society (1987) 890.<br />

[4] PESIC, S., Wave-plasma interaction near the second electron cyclotron harmonic, Phys. Fluids<br />

31 1 (1988) 115.<br />

[5] SHKAROFSKY, I.P., Dielectric tensor in Vlasov plasmas near cyclotron harmonics, Phys.<br />

Fluids 9 3 (1966) 561.

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