Digital data acquisition modules for instrumenting large segmented germanium detector arrays

XIA LLC has developed a 16-channel digital gamma-ray spectrometer (DGF Pixie-16) and associated electronics for instrumenting segmented germanium detector systems with large numbers of channels. The Pixie-16 is a CompactPCI/PXI-based data acquisition module equipped with 100 MHz 12-bit digitizers, signal processing field programmable gate arrays and a digital signal processor. Housed in a custom 6U PXI chassis, its operation can be extended to multiple chassis by using modules which distribute clock and triggers between chassis in LVDS format to achieve high speed and low distortion transmission. XIA LLC has collaborated with the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University in the construction of a fully Digital Data Acquisition System (DDAS) for instrumenting the 594-channel Segmented Germanium Array (SeGA) at NSCL. Using its gamma-ray tracking capability and consequently improved precision in determining gamma-ray interaction positions in the SeGA detectors, the DDAS will significantly improve their ability to determine gamma-ray emission angles and thus achieve better Doppler corrections. In this paper, we demonstrate the capability to achieve sub-nanosecond timing resolution when capturing waveforms in modules across multiple chassis in response to common global triggers. We then discuss the NSCL DDAS firmware solution, especially considering its capability for data acquisition with near zero dead times.