TH/P3-10 Electron Cyclotron Power Losses in Fusion Reactor-Grade Tokamaks: Scaling Laws for Spatial Profile and Total Power Loss

Potential importance of electron cyclotron (EC) wave emission in the local electron power balance in the steady-state regimes of ITER operation suggested analyzing in more detail the accuracy of calculating the 1D distribution, over magnetic flux surfaces, of the net radiated power density, PEC(ρ). Recent comparison of numeric codes SNECTR, CYTRAN, CYNEQ and EXACTEC for different electron temperature profiles and average temperatures of relevance for fusion reactor-grade magnetoplasmas, has shown good agreement of results within two different cases: (A) specular reflection in a circular cylinder (SNECTR, EXACTEC) and (B) diffuse reflection in a circular cylinder (SNECTR), and diffuse reflection in any geometry or any reflection in a noncircular toroid (CYTRAN, CYNEQ). These cases were shown to provide, respectively, the lower and upper bounds for PEC(ρ), including that for the modulus of PEC(ρ), inverted in sign in the plasma column periphery. Here we extend this analysis to show the following approximate scaling laws on the example of calculations with CYNEQ: (i) new formula for the volume-integrated EC power loss, , which gives a simplest extension of the Trubnikov’s formula, originally suggested for homogeneous electron density ne and temperature Te, to the case of ne and Te profiles expected for ITER and DEMO; (ii) the normalized profiles, PEC(ρ)/ , for identical normalized temperature profiles, Te(ρ)/, appear to be very close for substantially different volume-averaged temperatures, ; (iii) in the central plasma, profile PEC(ρ) in the case A may be close enough to that in the case B for larger value of wall reflectivity Rw, thus depending on an effective Rw, incorporating the type of reflection (diffusive or specular) and the geometry of the vacuum chamber. tot EC P