A Zynq-based flexible ADC architecture combining real-time data streaming and transient recording

Abstract

The RFX-mod2 Nuclear Fusion experiment is an upgrade of RFX-mod, shutdown in 2016. Among the other improvements in the machine structure and diagnostics, a larger number of electromagnetic probes (EMs) is foreseen to provide more information about plasma instabilities and to allow an improved real-time plasma control. An Analog to Digital Converter (ADC) architecture able to provide at the same time both transient recording and real-time streaming, as well as FPGA-based time integration of the inputs is foreseen in RFX-mod2. Transient recording provides full speed data acquisition (up to 1 MSample/s) by recording data in local memory and reading memory content after the plasma discharge. Real-time streaming of sub-sampled data is required for active control. The chosen technology is based on the XILINX Zynq architecture that provides in the same chip a multi-core ARM processor tightly coupled to a FPGA. Time critical functions are carried out by the FPGA, such as the management of the circular data buffer, low pass filtering for subsampling of the samples to be streamed and digital integration. Other functions are carried out by the processor, such as the management of the configuration setting, received via TCP/IP or HTTP, the data readout of acquired samples in transient recording buffers and network data streaming of data collected for active real-time plasma control.