New development of EPICS-based data acquisition system for millimeter-wave interferometer in KSTAR tokamak

After successful achievement of the first plasma in 2008, Korea Superconducting Tokamak Advanced Research (KSTAR) has performed the 4. campaign in 2011. During the campaigns, many diagnostic devices have been installed for measuring the various plasma properties in the KSTAR tokamak. From the first campaign, a data acquisition (DAQ) system of Millimeter-wave interferometer (MMWI) has been operated to measure the plasma electron density. The DAQ system at the beginning was developed for three different diagnostics having similar channel characteristics with a VME-form factor housing three digitizers in Linux OS platform; millimeter-wave interferometer, H-alpha monitor and ECE radiometer. However, this configuration made some limitations in operation although it had an advantage in hardware utilization. It caused unnecessarily increasing data acquired from the diagnostics when one of them operated at higher frequency. Moreover, faults in a digitizer led to failure in data acquisition of the other diagnostics. In order to overcome these weak points, a new MMWI DAQ system has been developed with a PXI-form factor in Linux OS platform and a control application has been developed on EPICS framework like other control systems installed in KSTAR. It also includes MDSplus interface for the pulse-based archiving of experimental data. Main advantages of the new MMWI DAQ system besides solving the described problems are capabilities of calculating plasma electron density during plasma shot and displaying it in run-time. To this end, the data can be provided to users immediately after archiving in MDSplus DB. (authors)