The main features of self-consistent pressure profile formation

Abstract

The self-organization of a tokamak plasma is a fundamental turbulent plasma phenomenon, which leads to the formation of a self-consistent pressure profile. This phenomenon has been investigated in the T-10 tokamak in different experiments, excluding profiles with pronounced transport barriers. It will be shown that the normalized pressure profile can be expressed by the equation p N (r) = p(r, t)/p(0, t), over a wide range of plasma densities. It will also be shown that p N (r) is independent of the heating power and the deposition profile of electron cyclotron resonance heating. Experiments show that p N (r) depends only on the value of q at the plasma edge. During rapid current ramp-ups it has been demonstrated that the conservation of p N (r) is established during a time t c < 0.1τ E , with τ E the energy confinement time. It can be concluded that the self-consistent pressure profile p N (r) in tokamaks is linked to the equilibrium of a turbulent plasma.

The role of ion and electron electrostatic turbulence in characterizing stationary particle transport in the core of tokamak plasmas

“…[17] and references therein). However, a systematic study of how their interplay produces the self-consistent steady-state from equation (13) has not yet been addressed in details. We will address this issue in the next sections using the linear limit of the theory, which is discussed in the following subsection.…”

“…The relative weight between the thermodiffusive part of the total normalized density gradient, namely −C T R/L Te , and the other contribution C P , is also changed with R/L Te . The temperature normalized gradients are set at: R/L Te = [5,7,9,11,13] and R/L Ti = [6, 9, 12]. > 0).…”

Chaotic transport in Hamiltonian systems perturbed by a weak turbulent wave field

“…The transport barrier formation near the low-order rational tori found numerically in Hamiltonian systems perturbed by a weak turbulent field at the large Kubo numbers, probably, may have some sort of relation to the transport barriers in fusion experiments (see, e.g., a review [4]). As was mentioned above there is a possible relation between the density of rational magnetic surfaces (or tori) and the transport of particles and energy, particularly, the transport barrier formation in fusion experiments, which has been already discussed in a number of papers [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Unlike qualitative arguments given in those works we have explicitly shown the formation of transport barriers in Hamiltonian systems by direct numerical calculations and explored the conditions at which such barriers are created.…”

“…7 in the whole region 0 < J < 1 for the large Kubo number K = 100 (a) and in the region 0.5 < J < 0.55 located near the rational tori ω = 1/3 for the several values of K = 1,2,5, and 100 (b). The values for the other parameters are chosen: q 0 = 0.8, q a = 5, γ ≡ 1, 20 n 50, and α = 5/6, which corresponds to the power spectrum |H mn | 2 ∼ n −5/3 , and the 1 The existence of gaps in the density of rational tori has been pointed out already in many above-mentioned works [15][16][17][18][19][20][21][22][23][24][25], however, no quantitative estimations have been presented. Moreover, I could not find the results obtained here in existing literature, although one could expect that this problem has been treated already in number theory or in other fields of physics.…”

“…At present several possible mechanisms, like an ExB flow shear, a zonal flow, or a magnetic shear, have been proposed. One of these issues is the role of low-order magnetic surfaces in the formation transport barriers which have been discussed in a number of works [12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”