Characteristics of an Energy-Resolving System Using Dynamic Time Over Threshold Method

The time over threshold (ToT) method can greatly simplify the data acquisition (DAQ) and control unit of a multichannel energy-resolving system. However, the system suffers from poor linearity. The linearity can be significantly improved by superimposing a delayed exponential rising voltage waveform over the constant preset threshold after the leading-edge triggering. This is called the dynamic time over threshold (DToT) method. In this paper, a theoretical model is proposed and verified by experimental results to characterize the noise transfer, integral nonlinearity (INL), and stability of a DToT-based system. The results show that the DToT system is able to achieve an INL of 2% or better over a wide dynamic range without outstanding increments of noise contributions to the energy resolution. Both the energy resolution and stability are significantly enhanced compared with those of a normal ToT system. We suggest that the DToT method can be applied to simplify the DAQ unit of a multichannel solid state detector system requiring medium energy resolution and linearity.