In the paper experimental study of charge division effects and energy resolution of X-ray silicon pad detectors are presented. The measurements of electrical parameters, capacitances and leakage currents, for six different layouts of pad arrays are reported. The X-ray spectra have been measured using a custom developed dedicated low noise front-end electronics. The spectra measured for six different detector layouts have been analysed in detail with particular emphasis on quantitative evaluation of charge division effects. Main components of the energy resolution due to Fano fluctuations, electronic noise, and charge division, have been estimated for six different sensor layouts. General recommendations regarding optimisation of pad sensor layout for achieving best possible energy resolution have been formulated.

We present the results of a systematic investigation of X-ray induced radiation damage in silicon pad sensors for total ionising doses up to 320 Gy (SiO2). The radiation induced degradation of energy spectra as well as of critical sensor parameters, capacitance and leakage current, have been measured vs total dose. Detailed analysis of the measured energy resolution shows that degradation of energy resolution can be explained by degradation of the sensor parameters. Additional radiation effects related to charge division have been observed.