Time decay constants of resistive detectors

Several authors have studied the dependence of the detection efficiency or charge gain of a resistive detector on the counting rate. Most of these results assume a stationary regime and treat the dielectric as equivalent to a simple RC circuit. In order to verify the validity of this model we have investigated the transient behavior of a resistive detector with a cylindrical geometry for various counting rates. In the present work we show that the charge-signal amplitude decays with time and tends towards a constant value that corresponds to the pulse height under stationary regime. In some cases the time-decay curves can be fitted by a single exponential plus a constant term, while in others (higher counting rates) a sum of two exponentials plus a constant term is needed to fit the experimental data. The time constants show a tendency to decrease with increasing counting rate that prevents us from relating these constants to the glass-relaxation mechanisms. However, these results indicate how fast the effective relaxation of the dielectric is and also demonstrate that the resistive detector cannot be treated as equivalent to simple RC circuits.