Maximising position resolution for near-simultaneous events with charge division readouts

Abstract

The maximum count rate of charge division readouts is fundamentally limited by the signal-to-noise ratio (SNR) required from the charge measurement electronics. The traditional charge measurement solution comprises a charge sensitive preamplifier, shaping amplifier and digitizer. The pulse processing time is limited by the shaping time constant required for a given SNR. We present a technique to measure event pulse heights from each readout channel using waveforms captured directly from the preamplifier output. This method uses signal analysis techniques, for example waveform fitting, to measure the charge collected by each readout channel, from several, almost simultaneous events. Given the signal processing requirements, this technique is suitable for applications where near-simultaneous events occur at relatively low-repetition rates. We discuss the signal analysis methods used and measure the achievable SNR ratio. We describe the preliminary experimental set-up, which uses a digital scope for waveform capture, and with data analysis carried out in PC-based software. We discuss the design of a system of dedicated electronics comprising dedicated waveform capture hardware and digital signal processing techniques. We provide estimates of the projected performance characteristics.