The Design and Performance of the Real-Time Software Architecture for the ITER Radial Neutron Camera

The neutron detection system for characterization of emissivity in ITER Tokamak during DD and DT experiments poses serious challenges to the performance of the diagnostic control and data acquisition system (CDAcq). The ongoing design of the ITER radial neutron camera (RNC) diagnostic is composed by 26 lines of sight (LOS) for complete plasma inspection. The CDAcq system aims at meeting the ITER requirements of delivering the measurement of the real-time neutron emissivity profile with time resolution and control cycle time of 10 ms at peak event rate of 2 MEvents/s per LOS. This measurement demands the generation of the neutron spectra for each LOS with neutron/gamma discrimination and pile-up rejection. The neutron spectra can be totally processed in the host CPU or it can use the processed data coming from the system field-programmable gate array (FPGA). The number of neutron counts extracted from the spectra is then used to calculate the neutron emissivity profile using an inversion algorithm. Moreover, it is required that the event-based raw data acquired are made available to the ITER data network without local data storage for postprocessing. The data production for the 2 MEvents/s rate can go up to a maximum data throughput of 0.5 GB/s per channel, fostering the evaluation of real-time data compression techniques in RNC. To meet the demands of the project, a CDAcq prototype has been used to design and test a high-performance distributed software architecture taking advantage of multicore CPU technology capable of coping with the requirements. This submission depicts the design of the real-time architecture, the spectra algorithms (pulse height analysis, neutron/gamma discrimination, and pile-up correction), and the inversion algorithm to calculate the emissivity profile. Preliminary tests to evaluate the systems performance with the synthetic data are presented.