Safety factor profile requirements for electron ITB formation in TCV

Abstract

On the Tokamakà Configuration Variable (TCV), electron internal transport barriers (eITBs) can be formed during a gradual evolution from a centrally peaked to a hollow current profile while all external actuators are held constant. The formation occurs rapidly (<τ eE) and locally and, according to ASTRA modelling, is consistent with the appearance of a local minimum in the safety factor (q) profile. The eITB is sustained by non-inductively driven currents (including the off-axis bootstrap current) for many current redistribution times while the current in the tokamak transformer is held constant. The maximum duration is limited by the pulse length of the gyrotrons. The transformer coil can be used as a counter (or co-) current source with negligible accompanying input power. In established eITBs the performance can be enhanced (degraded) by altering solely the central current or q-profile. New experiments show that the same stationary eITB performance can be reached starting from discharges with centrally peaked current. A fine scan in surface voltage shows a smooth increase in performance and no sudden improvement with voltage despite the fact that q min must pass through several low-order rational values.

The physics of electron internal transport barriers in the TCV tokamak

“…during the formation of the barrier or after the barrier was fully formed). With the aid of safety-factor profile modelling these results strongly suggested that rational q values do not play a role in the formation of the barrier, at least in the range 1.3 < q < 2.3 [6]. A conclusive proof would require a direct q-profile measurement.…”

“…This high sensitivity to power deposition results in a certain degree of variability between nominally identical scenarios. However, the robustness of the configuration is greatly increased when a significant amount of power is deposited deliberately well inside the barrier in order to exploit the high confinement and optimize the overall plasma performance [6].…”

“…Fully noninductive scenarios involve an appropriate distribution of current drive (ECCD) sources sustaining a hollow current profile, further enhanced by the bootstrap current centred in the high gradient barrier region [4][5][6][7]. Depending on the details of the discharge parameters and conditions, these scenarios may or may not evolve to a true steady state, whose duration is limited merely by equipment constraints and can equal several current redistribution times and up to hundreds of electron energy confinement times.…”

“…The operational recipes that have been established for generating eITBs depend on the accurate positioning ability of the launchers, as the properties and dynamic evolution of the discharge have been shown to be very sensitive to the heating locations and parallel wave numbers of the various beams [6,9,11]. The steerability of the launchers can then be employed to control the eITB performance in dynamically varying scenarios.…”

miR825 and miR825* function as negative regulators in Bacillus cereus AR156-elicited systemic resistance to Botrytis cinerea in Arabidopsis thaliana

“…The components of PTI include mitogen-activated protein kinase (MAPK) activation [3], defense-related gene expression, and callose deposition [2,4,5]. On the other hand, many pathogens secret multiple specific effectors to inhibit PTI in host plants [6][7][8], which, however, have developed the second line of defense comprising resistance (R) proteins that target corresponding pathogen effectors, resulting in effector-triggered immunity (ETI) [9] hypersensitive response (HR) at the infected site to inhibit the growth of biotrophic pathogens [1,2].…”