Development of slew-rate-limited time-over-threshold (ToT) ASIC for a multi-channel silicon-based ion detector

High-resolution Elastic Recoil Detection Analysis (HERDA), which consists of a 90 degrees sector magnetic spectrometer and a position-sensitive detector (PSD), is a method of quantitative hydrogen analysis. In order to increase sensitivity, a HERDA system using a multi-channel silicon-based ion detector has been developed. Here, as a parallel and fast readout circuit from a multi-channel silicon-based ion detector, a slew-rate-limited time-over-threshold (ToT) application-specific integrated circuit (ASIC) was designed, and a new slew-rate-limited ToT method is proposed. The designed ASIC has 48 channels and each channel consists of a preamplifier, a slew-rate-limited shaping amplifier, which makes ToT response linear, and a comparator. The measured equivalent noise charges (ENCs) of the preamplifier, the shaper, and the ToT on no detector capacitance were 253 +/- 21, 343 +/- 46, and 560 +/- 56 electrons RMS, respectively. The spectra from a Am-241 source measured using a slew-rate-limited ToT ASIC are also reported.