  The recent progress in high-temperature superconductor technologies has led
to the design and construction of SPARC, a compact tokamak device expected to
reach plasma breakeven with up to $25$MW of external ion cyclotron resonant
heating (ICRH) power. This manuscript presents local (flux-tube) and radially
global gyrokinetic GENE (Jenko et al 2000 Phys. Plasmas {\bf 7} 1904)
simulations for a reduced-field and current H-mode SPARC scenario showing that
supra-thermal particles - generated via ICRH - strongly suppress ion-scale
turbulent transport by triggering a fast ion-induced anomalous transport
barrier (F-ATB). The trigger mechanism is identified as a wave-particle
resonant interaction between the fast particle population and plasma
micro-instabilities (Di Siena et al 2021 Phys. Rev. Lett. {\bf 125} 025002). By
performing a series of global simulations employing different profiles for the
thermal ions, we show that the fusion gain of this SPARC scenario could be
substantially enhanced up to $\sim 80\%$ by exploiting this fast ion
stabilizing mechanism. A study is also presented to further optimize the
energetic particle profiles, thus possibly leading experimentally to an even
more significant fusion gain.
