COTS-Based High-Data-Throughput Acquisition System for a Real-Time Reflectometry Diagnostic

Achieving higher levels of plasma performance control in present fusion experiments requires that diagnostics be upgraded to deliver processed physical parameters in real time (RT). A key element in a diagnostic RT upgrade is the data-acquisition system (DAS) that should be capable of delivering the acquired data to the data-processing resources with very low latencies and in the shortest possible time. Adequate standard commercial solutions with these characteristics are not easily found in the market, which leads most of the time to the development of complex custom high-performance designs from ground-up. A mixed solution, partially based on commercial off-the-shelf (COTS) components has been developed to upgrade the existing ASDEX upgrade broadband reflectometry diagnostic so that a full demonstration of plasma position control using RT reflectometry density profile measurements can be performed. The designed 8-channel (12-bit/105 MSPS) DAS features a PCI Express 1.1 (PCIe) x8 interface to enable direct memory access (DMA) data transfers with an effective throughput in excess of 1 GB/s. The use of COTS components resulted in a faster hardware design cycle without compromising system performance and flexibility. The architecture of the system and its main design constraints are herein discussed. Benchmark results for data throughput and overall latency measurements are also presented.