The LANL Neutron Science Center TOF/PSD module: status and progress

This paper describes the progress and current status of a joint collaboration between Argonne National Laboratory (ANL) and the Los Alamos National Laboratory (LANL) Manuel Lujan Neutron Science Center (MLNSC) to develop and implement a time-of-flight/position-sensitive-detector (PSD) VXI-based C-size neutron-event data-collection module. The LANL module, based on the ANL-developed hardware which uses field-programmable gate arrays (FPGAs) and analog-input-signal conditioning modules for a flexible topology capable of accepting either eight or 16 input channels, has been reprogrammed and modified to incorporate more LANL-specific features such as improved peak detection, 24-bit time stamps, and 16-bit channel identification numbers which are all part of a 64-bit event record (2 by 32-bits wide). Using a backplane 10-MHz clock, timing resolution is /spl plusmn/50 ns. The module uses two frame FIFOs, each 2-kwords deep, to accumulate event data at up to. 330 kEvents/sec during a frame until the host CPU can read it out. One FIFO is read while the other is being filled. The module does not use the ANL token-passing configuration for accessing data. Rather, it uses direct logical-address and register-based addressing modes. To interface with analog signals from the neutron detectors, the module incorporates eight 72-pin SIM-size interface modules which contain differential receivers, analog threshold comparators, and 8-bit analog-to-digital converters. A total of 16-analog channels are available if used in TOF mode, or eight channels if used in PSD mode. The FPGAs have been programmed to interface, control, and read data from the interface modules.