Data Acquisition in the ITER Ion Source Experiment

The Ion Source experiment, called SPIDER, is the first experiment to be realized in the ITER Neutral Beam Test Facility under construction at Consorzio RFX, Padova, Italy. Its data acquisition system will provide the collection of around one thousand signals at a sampling rate ranging from a few S/s to 10 MS/s and of diagnostics and inspection images produced at a frame frequency from 10 to 150 frame per second, for beam durations of up to one hour. As the final product of the Test Facility will be the ITER Heating Neutral Beam Injector, we decided to follow the ITER CODAC guidelines. Therefore, the EPICS system provided in the CODAC Core System has been assessed and adopted in plant control. In addition to EPICS, the MDSplus system will be adopted for the overall data management. MDSplus can handle a rich set of data types and offers support for both local and remote data access in a variety of languages, a feature not fully supported by EPICS. All experiment data in SPIDER will be maintained in a single MDSplus database containing both experiment configuration and acquired data. The seamless integration of EPICS and MDSplus in a single system requires the development of some new tools, namely: A Channel Archiver which provides storage into MDSplus pulse files of data produced by EPICS Input Output Controllers (IOC) and exported as Process Variables via Channel Access; A set of IOC records providing direct access from IOC into MDSPlus files; A Channel Access Server to export MDSplus data as EPICS Process Variables, making them directly accessible by IOCs. We expect that the integration of the two frameworks will result in a system that combines the best features from each one, i.e., the management of distributed Process Variables and the IOC concept for EPICS, the sophisticated data management and remote access for MDSplus.