The LANL Neutron-Science-Center Time-Of-Flight/Position-Sensitive-Detect module: Status and progress

This paper describes the progress and current status of a joint collaborati on between Argonne National Laboratory (ANL) and the Los Alamos National La boratory (LANL) Manuel Lujan Neutron Science Center (MLNSC) to develop and implement a Time-of-flight (TOF)/Position-Sensitive-Detector (PSD) VXI-base d C-size neutron-event data-collection module. The LANL module, based on the ANL-developed hardware which uses field-progr ammable gate arrays (FPGAs) and analog-input-signal conditioning modules fo r a flexible topology capable of accepting either eight or 16 input channel s, has been programmed and modified to incorporate more LANL-specific featu res 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 3 2-bits wide). Using a backplane 10-MHz clock, timing resolution is +/-50 ns . The module uses two, frame first-in-first-out buffers (FIFOs), each 2-kwo rds deep, to accumulate event data at up to 330 kEvents/sec during a frame until the host computer can read it out. One FIFO is read while the other i s being filled. The module does not use the ANL token-passing configuration for accessing d ata. Rather, it uses direct logical-address and register-based addressing m odes. To interface with analog signals fi-om the neutron detectors, the mod ule incorporates eight 72-pin single-inline-memory-module-size plug-in boar ds, called SIMs, which contain differential receivers, analog threshold com parators, and 8-bit analog-to-digital converters. A total of 16-analog chan nels are available if used in TOF mode, or eight channels if used in PSD mo de.