  The IceCube Collaboration foresees to upgrade IceTop, the present surface
array, with scintillator detectors augmented by radio antennas. As one of
several goals the scintillator detectors will be used to measure and mitigate
the effects of snow accumulation on the IceTop tanks: the increasing energy
threshold and efficiency loss are nowadays the sources of the largest
systematic uncertainties in shower reconstruction and mass composition
analysis. In addition, the upgrade will provide useful experience for the
development of next generation neutrino detectors proposed for the South Pole.
In the Austral summer season, 2017-2018 two full "stations" were installed near
the center of the IceTop array. Each station features custom-designed
electronics and consists of seven detectors, each having an active area of
1.5m$^{2}$ plastic scintillator and wavelength shifting fibers read out by a
Silicon Photomultiplier. In this contribution we review the detector design and
performance, and show results from more than one year of operation of the
prototype stations. During that year several thousand air shower events have
been measured in coincidence with IceTop.

High Energy Astrophysical Phenomena;Instrumentation and Methods for Astrophysics