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A novel real time fast electron bremsstrahlung (FEB) diagnostic system based on the lutetium yttrium oxyorthosilicate scintillators (LYSO) and silicon photomultipliers (SiPM) has been developed for tokamak. The diagnostic system is dedicated to study the FEB emission in the hard x-ray (HXR) energy range between 10 and 200 keV during the lower hybrid current drive. The system consists of a detection module and three data acquisition and processing (DAP) boards. The detection module consists of annulus LYSO-SiPM detector array and a 12-channel preamplifier module. The DAP boards upload the data to the host computer for displaying and storing through PXI bus. The time and space resolutions of the system are 10 ms and 4 cm, respectively. The experimental results can show the evolution over time and the spatial distribution of FEB. This paper presents the system performance and typical discharge results.

In the real-time plasma electron density measurement using far infrared (FIR) laser interferometry, the plasma electron density can be calculated by measuring the real time phase difference between the reference signal and the probe signal. A novel Real-time Phase Jump Process (RPJP) method is applied to the HL-2A tokamak. With this method, the phase difference precision is up to 1 3600 fringe (1 fringe is equal to a phase shift of 2π), and the dynamic measurement range is extensible 65536 fringes. The time resolution of the phase difference is 80 ns, while the feedback delay is 180 µs.

Electron density and Faraday rotation angle are important physical parameters in nuclear fusion research. To measure them simultaneously, the three-wave polarimeter/interferometer diagnostic system is applied. Both the final probe output signal and the reference signal contain three frequency components. The time-varying phase difference curve of each frequency component can be measured by the Real-time Dynamic Spectrum Analysis (RDSA) method based on Field-Programmable Gate Array (FPGA). The phase difference precision is better than 0.1 o and the real-time feedback delay is less than 1 ms, which satisfy the requirements of HL-2A.

A new neutron-gamma discriminator based on the support vector machine (SVM) method is proposed to improve the performance of the time-of-flight neutron spectrometer. The neutron detector is an EJ-299-33 plastic scintillator with pulse-shape discrimination (PSD) property. The SVM algorithm is implemented in field programmable gate array (FPGA) to carry out the real-time sifting of neutrons in neutron-gamma mixed radiation fields. This study compares the ability of the pulse gradient analysis method and the SVM method. The results show that this SVM discriminator can provide a better discrimination accuracy of 99.1%. The accuracy and performance of the SVM discriminator based on FPGA have been evaluated in the experiments. It can get a figure of merit of 1.30.