# Optimized up-down asymmetry to drive fast intrinsic rotation in tokamaks

## TL;DR

This paper demonstrates that optimizing the shape of flux surfaces in tokamaks by tilting elongation and triangularity can significantly enhance intrinsic rotation, potentially stabilizing MHD instabilities with minimal energy transport.

## Contribution

The study introduces a method to optimize flux surface shapes with tilted elongation and triangularity to maximize intrinsic rotation in tokamaks.

## Key findings

- Adding tilted triangularity doubles momentum transport.
- Optimized shape can generate rotation sufficient to stabilize instabilities.
- Rotation achieved is four times larger than in standard ITER conditions.

## Abstract

Breaking the up-down symmetry of the tokamak poloidal cross-section can significantly increase the spontaneous rotation due to turbulent momentum transport. In this work, we optimize the shape of flux surfaces with both tilted elongation and tilted triangularity in order to maximize this drive of intrinsic rotation. Nonlinear gyrokinetic simulations demonstrate that adding optimally-tilted triangularity can double the momentum transport of a tilted elliptical shape. This work indicates that tilting the elongation and triangularity in an ITER-like device can reduce the energy transport and drive intrinsic rotation with an Alfv\'{e}n Mach number on the order of $1\%$. This rotation is four times larger than the rotation expected in ITER and is sufficient to stabilize MHD instabilities. It is shown that this optimal shape can be created using the shaping coils of several experiments.