  It is shown that for moderately hot polar caps (with effective temperature of
$\sim 10^6$ K), the efficiency of polar gap acceleration is lower compared to
the case in which the polar caps are relatively cool and inverse Compton
scattering plays no role in controlling the gap. For young pulsars with
superstrong magnetic fields ($\geq10^9 T$) and hot polar caps (with temperature
of $\ge 5\times10^6 K$), because of the energy loss of electrons or positrons
due to resonant inverse Compton scattering in the vicinity of polar caps, pair
cascades occur at distances further away from the polar cap, and in this case,
we have a relatively high acceleration efficiency with ions carrying most of
the particle luminosity.
