Design, development and testing of real time control and data acquisition system for R&D IC H&CD source

One of the important auxiliary heating and current drive systems for ITER experiment is Ion Cyclotron Heating & Current Drive (IC H&CD) system. ITER requires 1 prototype and 8 independent RF Sources, each having capability to deliver constant output power of 2.5 MW at VSWR 2 in the frequency range of 35-65 MHz. To meet the ITER requirement, an R&D program has been launched to identify the final stage tube (Tetrode/Diacrode) for MW level RF amplifier, along with other critical components. Under this R&D program, single chain of RF cascaded amplifiers, consisting of low & high power RF sections, auxiliary power supply, Anode power supply and test bench simulating ITER requirement, are being developed. To ensure reliable and safe operation of the entire system, PLC/PXI based Local Control Unit (LCU) is developed. PLC based sequential control system is developed for sequential biasing of electrodes of high power vacuum tubes (Tetrode/Diacrode). To protect the RF Source against critical fault condition, local protection logic is developed using PXI-7841R, which will ensure fast shut off (<10 μs) of RF and power supplies. Constant and stable power output even with variable load condition (up to VSWR 2) is achieved by employing two real time feedback control loops-one for making constant output power and the other one for optimizing anode & screen grid dissipation. For fault/offline analysis, event based acquisition and logging functionality is provided that acquires and logs data at 1 μs sampling rate for 100 ms pre and post time. During the RF Shot, normal acquisition and logging for all channels are provided with 1 ms sampling rate. Further, online display for user selectable 8 channels is provided. All the operational and monitoring parameters are continuously updated on Main screen to give the real time status of the system. In this paper, salient feature of R&D LCU and test results are discussed in detail.