Development of a shaping amplifier, gated integrator and 16 K Channel ADC for a portable spectroscopy system

Fieldable, portable spectroscopy systems which provide 16 K channel space with high resolution and which can operate for long periods of time on readily available batteries are a valuable tool for environmental monitoring and non-proliferation applications. A low power portable spectroscopy system for use with a 100% n-type HPGE detector was recently completed by Constellation Technology Corporation. This system provides 16 K channel resolution while consuming under 1.3 W. A major component of this system, the ADC board assembly, implements a semi-Gaussian shaping amplifier, gated integrator, and analog-to-digital converter (ADC) to perform analog pulse processing and amplitude digitization of charge pulses from the detector preamplifier. All functions of the board are implemented onto a 4″×6″ circuit board using commercially available components. The board exhibits an integral non-linearity of less than ±0.015% over the top 99% of 16 K channels and a combined offset and gain temperature coefficient of 52.9 ppm/°C over a −25 to +85 degree Celsius temperature range. The power consumption for the board while converting at 10 kHz is 460 mW.