Performance of a High Speed and High Density Data Acquisition System for Multiple Gamma-ray Detection

To accelerate the data acquisition system (DAQ), which was reported in NSS 2004[1], the authors improved the Main ADC Modules in the DAQ. The new Main ADC Module has 8 input channels. Each channel consists of analog circuits for pulse shaping, a high-speed ADC (14bit 125MSPS), and a high-power Digital Signal Processor (DSP: 8000MIPS). Shaped input signals are digitized with the ADC and analyzed by the DSP to calculate the energy data. Total energy resolution of this system was 2.5 keV in FWHM for 1.33-MeV gamma rays. Time resolution of this system was 120 ns in FWHM between two Ge detectors. These results show good performances as a conventional DAQ. The dead time of this system is only 4.3 us per event and the maximum event rate was more than 350k events/s. Thus, enough energy and time resolutions are achieved with short dead time, high channel density and high event rate.