Application of dynamic time over Threshold method to germanium detector

Time over Threshold readout is suitable for multichannel system because of its circuit simplicity, low power consumption and binary readout compared with conventional pulse height measurement. But the ToT measurement suffers from the non-linearity problem. We developed a dynamic Time over Threshold method with trapezoidal shaping for better linearity. The circuit consists of delay line clipping and integrator. The crossing with the trapezoidal shaped signal and ramp threshold signal generates the linear relation with the input charge and time over threshold. The measured Integrated Non-Linearity (INL) is 1% for this method. We have applied dynamic ToT method to the germanium detector to validate the principle. The measured energy resolution @511keV with 22Na source is 0.8% for normal Pulse Height Analysis (14bits ADC) and 1% for Dynamic Time over Threshold Method with trapezoidal shaping.