We present a 32-channel data acquisition system using the PSEC4A chip and initial applications as a readout system for neutron detectors at Sandia’s Z Pulsed-Power Facility. The PSEC4A is an 8-channel, 10 GSa/s waveform recording ASIC with an analog bandwidth of 1.9 GHz, which also incorporates multi-event buffering to reduce latency induced by close-in-time triggers. In the 32-channel system, four PSEC4As are time synchronized using a common clock delivered from a PLL chip. Triggering can be done using the internal PSEC4A discriminators or via an external input. An optical serial communication link serves as the user interface to the board.
The PSEC4A ASIC, as reported at TWEPP-18, was designed and fabricated in 2017 as an upgrade to the PSEC4 waveform sampling chip. The PSEC4 offers 10 GSa/s sampling rates, self-triggering, and high bandwidth, but its scope is limited due to a short 256-sample recording length on each channel. To address this issue, PSEC4A combines the PSEC4 digital circuitry with a new analog design, which allows a larger recording window as well as the option for multi-event partitioning of the analog buffer, while keeping high analog bandwidth.
The 32-channel board uses four 8-channel PSEC4A ASICs, with each channel fed from a high-density Samtec (SEAF8) board-to-board connector that mates to the sensor board. The four PSEC4As are synchronized to the same clock through a PLL/jitter-cleaner chip, which may be referenced to an on-board oscillator or an external clock input. The system uses a low-cost Cyclone-V FPGA for system control and data management. To enable operation in the high-EMI environment at the Sandia Z Pulser-Power Facility, the board requires significant shielding and an isolated user interface over optical fiber. The PSEC4A board is designed to a compact size of 70mm by 106mm.
The sensor board is composed of an array of fast scintillator/SiPM detectors. The detector array is designed to measure the total flux and arrival time of 2.45 MeV fusion neutrons produced by deuterium-deuterium interactions in a high temperature plasma. The system can be used in either a particle counting mode for low fluence or in current mode for high fluence. The system response will be measured using a neutron calibration end station at Sandia’s Ion Beam Laboratory (IBL). This calibration facility uses the IBL’s 300-keV Cockroft-Walton generator to accelerate D+ ions to 175 keV, producing approximately 2.7 μA of beam current onto a 2.5-μm thick ErD2 target. The PSEC4A/SiPM system response will be compared with a standard scintillator/MCP-Photomultiplier/transient-digitizer neutron diagnostic. The PSEC4A system is being constructed for use as a compact and modular neutron time-of-flight (nTOF) spectrometer for Magneto Inertial Fusion (MIF) experiments.