Charge collection efficiency and resolution of an irradiated double-sided silicon microstrip detector operated at cryogenic temperatures

This paper presents results on the measurement of the cluster shapes, resol ution and charge collection efficiency of a double-sided silicon microstrip detector after irradiation with 24 GeV protons to a fluence of 3.5 x 10(14 ) p/cm(2) and operated at cryogenic temperatures. An empirical model is pre sented which describes the expected cluster shapes as a function of depleti on depth, and is shown to agree with the data. It is observed that the clus ters on the p-side broaden if the detector is under-depleted, leading to a degradation of resolution and efficiency. The model is used to make predict ions for detector types envisaged for the LHC experiments. The results also show that at cryogenic temperature the charge collection efficiency varies depending on the operating conditions of the detector and can reach values of 100% at unexpectedly low bias voltage. By analysing the cluster shapes it is shown that these variations are due to changes in depletion depth. Th is phenomenon, known as the "Lazarus effect", can he related to similar rec ent observations on diode behaviour. (C) 2000 Elsevier Science B.V. All rig hts reserved.