  We investigate the confinement properties of two recently devised
quasi-helically symmetric stellarator configurations, HSK and QSTK. Both have
been optimized for large critical gradients of the ion temperature gradient
mode, which is an important driver of turbulent transport in magnetic
confinement fusion devices. To predict the resulting core plasma profiles, we
utilize an advanced theoretical framework based on the gyrokinetic codes GENE
and GENE-3D, coupled to the transport code TANGO. Compared to the HSX
stellarator, both HSK and QSTK achieve significantly higher core-to-edge
temperature ratios, partly thanks to their smaller aspect ratios, with the
other part due to more detailed shaping of the magnetic geometry achieved
during optimization. The computed confinement time, however, is less sensitive
to core temperature than edge temperature, simply due to the disproportionate
influence the edge has on stored plasma energy. We therefore emphasize the
possible benefits of further optimizing turbulence in the outer core region,
and the need to include accurate modelling of confinement in the edge region in
order to assess overall plasma performance of turbulence optimized
stellarators.
