Systematische Untersuchungen zur Strahlenresistenz von Silizium-Detektoren für die Verwendung in Hochenergiephysik-Experimenten

The very intense radiation fields connected with the high energy and the high luminosityof future colliding beam machines (LHC, SSC) make the radiation hardness of all detectorcomponents an urgent requirement. In this thesis the radiation hardness of silicondetectors in high energy physics experiments was investigated systematically. Because ofthe mixed radiation field the particle and energy dependence were especially studied withmonoenergetic particles. These data show that the bulk damage corresponds independentlyof the particle type to the damage functions of the non ionizing energy loss, if theenergy of the energy of the primary knock-on atom is above a threshold value. In mostapplications the damage effects are dominated by the neutron induced bulk damage, andthe damage efficiency of the expected neutron spectrum corresponds to that of 1 MeVneutrons. Accordingly the damage functions were used for the normalization of differentradiation fields to 1MeV neutrons. With respect to the detector performance detailedmeasurements of the change in the effective donor concentration, the leakage current increaseand charge collection deficiency were investigated as function of the particle fluenceand the time after irradiation. Special emphasis was put on the self annealing effects atroom temperature in order to separate the respective damage generation and its subsequentself annealing. The change in the effective donor concentration is caused by donorand acceptor removal and radiation induced acceptor like centers. For n-type silicon thisleads to the conversion to p-type material, which was here, for the first time, proved withshort ranged a-particles. Also a modification of defects was observed during the long termself annealing leading to a further creation of acceptor like centers. The radiation inducedleakage current depends on the conduction type. Taking the self annealing into accountthe current increase in long term exposure is governed by a damage rate of 4.10-17 Acm-1•The charge collection efficiency for mip's was calculated from the electron and hole trapping,which was studied separately. The analysed results were discussed with respect toa long term behaviour in the intense radiation field of a high energy physics experiment.Based on the present results this discussion indicates that the radiation hardness of silicondetectors is sufficiently high to ensure operability for applications presently considered forfuture colliding beam machines