Parametric dependencies of ion temperature profile peaking in ASDEX Upgrade high-beta scenarios

Abstract Advanced Tokamak (AT) scenarios are attractive candidates for future nuclear fusion power plants. These scenarios often feature peaked temperature profiles, suggesting a local reduction of turbulent transport. The mechanisms behind this are, as yet, not fully understood. Parameters that are thought to be connected to these transport reductions include the q -profile and the E × B -shear <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>ω</mml:mi> <mml:mrow> <mml:mi>E</mml:mi> <mml:mo>×</mml:mo> <mml:mi>B</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> . Another parameter considered to be important is the fast ion content, which can reduce transport in multiple different ways. This work presents AT experiments performed at the ASDEX Upgrade tokamak (AUG) in which these three parameters are varied to investigate their respective effect on the observed peaked ion temperature profiles. To disentangle potentially competing effects, simulations using the codes GENE and TGLF have been performed. It is found that the E × B -shear does not play a role in the AT scenarios performed at AUG, which have relatively low rotation, with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>v</mml:mi> <mml:mrow> <mml:mi>tor</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>100</mml:mn> <mml:mo>−</mml:mo> <mml:mn>250</mml:mn> <mml:mstyle scriptlevel="0"/> </mml:mrow> </mml:math> km h −1 . Experimentally, a significant dependence of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mpadded depth="0" height="0"> <mml:mrow> <mml:mpadded depth="-2.8pt" height="+2.8pt"> <mml:mstyle displaystyle="false" scriptlevel="0"> <mml:mrow> <mml:mstyle mathsize="0.85em"> <mml:mtable columnalign="left" displaystyle="true"> <mml:mtr> <mml:mtd> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> </mml:mrow> </mml:mrow> </mml:mtd> </mml:mtr> </mml:mtable> </mml:mstyle> </mml:mrow> </mml:mstyle> </mml:mpadded> </mml:mrow> </mml:mpadded> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mpadded depth="0" height="0"> <mml:mrow> <mml:mpadded depth="+2.3pt" height="-2.3pt"> <mml:mstyle displaystyle="false" scriptlevel="0"> <mml:mrow> <mml:mstyle mathsize="0.85em"> <mml:mtable columnalign="left" displaystyle="true"> <mml:mtr> <mml:mtd> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">i</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:mrow> </mml:mtd> </mml:mtr> </mml:mtable> </mml:mstyle> </mml:mrow> </mml:mstyle> </mml:mpadded> </mml:mrow> </mml:mpadded> </mml:mrow> </mml:mrow> </mml:math> on the electron cyclotron current drive settings was found, indicating that either the current profile (and, therefore, the q -profile) or <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mpadded depth="0" height="0"> <mml:mrow> <mml:mpadded depth="-2.8pt" height="+2.8pt"> <mml:mstyle displaystyle="false" scriptlevel="0"> <mml:mrow> <mml:mstyle mathsize="0.85em"> <mml:mtable columnalign="left" displaystyle="true"> <mml:mtr> <mml:mtd> <mml:mrow> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>e</mml:mi> </mml:mrow> </mml:mrow> </mml:mtd> </mml:mtr> </mml:mtable> </mml:mstyle> </mml:mrow> </mml:mstyle> </mml:mpadded> </mml:mrow> </mml:mpadded> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mpadded depth="0" height="0"> <mml:mrow> <mml:mpadded depth="+2.3pt" height="-2.3pt"> <mml:mstyle displaystyle="false" scriptlevel="0"> <mml:mrow> <mml:mstyle mathsize="