Latency and throughput of online processing in Soft X-Ray GEM-based measurement system

The paper presents latency and performance study of the monitoring system for plasma impurities radiation in a tokamak. The developed solution measures radiation in Soft X-Ray range and can provide valuable information about the ongoing experiment with low latency. This work presents the test configuration with a single-dimensional pixel topology, with 64 channels, tested at photon rate about 100 kHz per channel. The hardware consists of the GEM-based detector, FPGAs, PCIe transmission system and the computer system with 64-bit x86 architecture. The software is the C/C++ code optimized for the execution time and working in the global trigger mode. The system uses raw data acquisition and the backend computations in CPU to provide high accuracy and high-quality results, not easily achievable otherwise. The research includes measurements of the throughput of the system and the latency of the whole data path - between the pulse detection in FPGA and storing of spectroscopy histograms in the file system in memory. The direction of improvements and further development were proposed.