Cosmic Ray Results from the IceTop Air Shower Array

IceTop, the surface component of the IceCube neutrino telescope at the South Pole, is an air-shower array which will finally consist of 160 ice Cherenkov tanks at 80 stations spread over an area of 1 km. Currently 40 stations are deployed and taking data. The detector is designed to cover the energy range above the knee up to about 10 eV and study the mass composition of primary cosmic rays. In this talk the performance of IceTop, the development of shower reconstruction algorithms and first results obtained with an array of 26 stations installed in 2007 will be reported. Preliminary results are presented for the cosmic ray energy spectrum in the range of 1 PeV to 100 PeV. Due to the atmospheric depth of only 700 g/cm at the altitude of the South Pole, a high sensitivity of the zenith angle distribution to the mass composition is observed. The main advantage of IceTop compared to other detectors in this energy range, is the possibility to measure high energy muons from air showers in coincidence with the in-ice detector. The muon rate at a given air shower energy is a very sensitive tool to measure mass composition. The prospects of this method and alternative methods of counting muons, in order to scrutinize different shower models, will also be presented.