  Pixel detectors are used in the innermost part of multi purpose experiments
at the Large Hadron Collider (LHC) and are therefore exposed to the highest
fluences of ionising 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 to establish such a limit, pixel
sensors of the size of one CMS pixel readout chip (PSI46V2.1) have been bump
bonded and irradiated with positive pions up to 6E14 Neq/cm^2 at PSI and with
protons up to 5E15 Neq/cm^2. The sensors were taken from production wafers of
the CMS barrel pixel detector. They use n-type DOFZ material with a resistance
of about 3.7kOhm cm and an n-side read out. As the performance of silicon
sensors is limited by trapping, the response to a Sr-90 source was
investigated. The highly energetic beta-particles represent a good
approximation to minimum ionising particles. The bias dependence of the signal
for a wide range of fluences will be presented.
