Test beam results on single-sided irradiated silicon microstrip detectors

Test beam results on irradiated AC-coupled, poly biased, single sided ( P+/N bulk) silicon microstrip detectors are presented. Detectors were fabricated at SINTEF ( Oslo, Norway); they have 128 strips, strip pitch of 50um, strip width of 12.5um and length of 5.5 cm. Neutron doses were 1*10^13 and 3.6*10^13 n/cm^2 and we estimated the gamma dose from the neutron irradiation facility background to be enough to induce full saturation in the oxide trapped charge value. Reverse-annealing processes were accelerated via heat treatment to ensure stable operational depletion and leakage current values during data taking. Three modules were contructed, one for each value of neutron dose, and one with non irradiated detectors using two crystals bonded together to form a 11cm long readout unit for each of the modules. Data was taken at room temperature using the CERN 120 GeV pion beam at X7 for different beam angle of incidence ( 0, 20, 35) as a function of Vbias up to values of 330V. For the most irradiated module we also took data with 100um readout pitch ( alternate readout scheme) at 330V. No appreciable performance losses were observed for these levels of radiation damage as long as the detectors could be operated at suitably high bias voltages.