Radiation hardness of CMS pixel barrel modules

Pixel detectors are used in the innermost part of multi purpose experiments at LHC and are therefore exposed to the highest fluences of ionizing radiation, which in this part of the detectors consists mainly of charged pions. The radiation hardness of the detectors has thoroughly been tested up to the fluences expected at the LHC. In case of an LHC upgrade, the fluence will be much higher and it is not yet clear up to which radii the present pixel technology can be used. In order establish such a limit, small pixel barrel sensors have been bump-bonded to CMS pixel read out chips. These samples have been irradiated with positive pions at PSI up to 6E14 Neq/cm2 and with 21 GeV protons at CERN up to 4E15 Neq/cm2. The effect of the radiation on both the sensor and the readout chip has been tested. The signal collection of the sensors and the analogue performance of the readout chip as a function of the irradiation fluence will be presented.