Real-Time Controller for Research and Development on ITER Ion Cyclotron Heating and Current Drive Source

Abstract

IndianDomestic Agency is responsible for the development and delivery of total nine numbers of RF sources for ITER ion cyclotron heating and current drive (ICH and CD) system. To validate the design of RF amplifier source, a research and development program has been initiated. Each ICH and CD source consists of two chains of amplifier, and each chain composed of low-power RF section, one solid-state power amplifier followed by two cascaded tunable high-power tube (tetrode/diacrode)-based amplifiers, high-voltage/high-current power supplies, and control system. A dedicated data acquisition and control system has been developed based on real-time (RT) PXI controller. To demonstrate the performance of RF source as required by ITER, two RT control for anode voltage regulation and voltage standing wave ratio (VSWR) for maintaining constant load power is implemented on field-programmable gate array (FPGA) module. To protect high-power RF tubes and related subsystems, interlock logic is implemented on another FPGA module, which will suppress RF input drive and switch off different biasing power supplies within $10~\mu \text{s}$ . To operate RF amplifier as per experimental requirement, user settable parameters ( $T_{\mathrm{\scriptscriptstyle ON}}- T_{\mathrm{\scriptscriptstyle OFF}}$ time, number of pulses, allowed number of faults before terminating the pulse, and rise time and fall time) for RF pulse generation are incorporated into application software developed using LabVIEW platform. Two modes of data acquisition function are implemented using NI PXI-8108 RT controller (embedded real time operating system controller). All analog and digital signals for status and health monitoring of different subsystems, normal acquisition mode having 1-ms sampling rate, are implemented. For fault analysis purpose, data are acquired with 1- $\mu \text{s}$ sampling frequency in trigger mode of acquisition with 100-ms predata and 100-ms postdata considering fault event as trigger for the acquisition. In this paper, architecture of RT controller is discussed in detail and various operational results are presented.