ATCA Fast Data Acquisition & Processing System for JET Gamma-Ray Cameras Upgrade Diagnostic
Nuclear reaction gamma-ray diagnosis is one of the important techniques used for studying confined fast-ions. The Joint European Torus (JET) gamma-ray camera diagnostic provides information on the spatial distribution of fast ions. The system is currently being upgraded and should allow gamma-ray image measurements in high power deuterium JET pulses, and eventually in deuterium-tritium discharges. In order to fully exploit the diagnostic capabilities it is mandatory to develop a reliable, maintainable, multi-channel spectroscopy Data Acquisition and real-time Processing (DAQP) system, which shares much of the common development for other specific implementation like Gamma-ray spectroscopy. The DAQP system is based on the Advanced Telecommunications Computing Architecture (ATCA) and contains a 6 GFLOPS x 86-based control unit and three Transient Recorder and Processing (TRP) modules, to cope with the two arrays of collimators (10 horizontal + 9 vertical lines of sight), interconnected through PCI Express (PCIe) links. Each TRP module features 8 channels of 13 bit resolution sampling at 250 MHz, 4GByte of local memory and two field programmable gate arrays able to perform complex trigger managing modes and allowing real time analyses (pulse height analyzer and pile-up discrimination), minimizing data storage and transfer issues. The DAQP system aims at overcoming the problem of storing large amount of data during long discharges. A raw/processed mode is being developed where the acquired raw data follows two parallel paths: besides being directly stored in the on-board memory, it is processed and streamed in real-time through PCIe links. This procedure is expected to greatly reduce the amount of data and possible allow continuous operation of the diagnostic. During commissioning and when data validation is required, the 4GB raw data will be executed on the x86 control unit through a well known algorithm and the result cross checked with the processed data.