Optimization Of Diagnostic Neutral Beam Power Supply System On J-TEXT

Diagnostic neutral beam, abbreviated DNB, is the core of charge exchange recombination spectroscopy diagnostic system which can be used to diagnose the important parameters, such as plasma ion temperature and rotation. DNB power supply system is the foundation of generation of neutral beam, and its working conditions directly affect the operating status of DNB system.The DNB power supply system on J-TEXT includes one set of high voltage power supply and one set of low voltage power supply system which consists of filament power supply, arc power supply, buffer bias power supply, suppressing power supply and deflecting magnet power supply. And they are the key of generating ions and neutral beam. After several years of operation, the output specification of the old DNB low voltage power supply system become poor, and malfunctions frequently occur. The old DNB low voltage power supply system can not satisfy the demand of normal running of DNB, so the upgrade of the DNB low voltage power supply system is carried out in this thesis. With the principle of DNB ion source hot cathode electron emission and gas ionization, the properties of corresponding components of ion source is analyzed and the demand of filament and arc power supply is given. With the experimental tests and the principles of the old DNB low power supply system, the failure reason has been foud out. Further more the digital control is proposed to improve the power supplys.Around digital control scheme, the paper presents the main circuit diagram of the optimized DNB low voltage power supply. Based on the main circuit diagram, the actual demand of DNB power supply and digital signal processor abbreviated DSP in the DNB low voltage power supply system based on the PI regulator feedback control strategy is proposed. All power supplies output waveform can be set via the upper computer, and these waveform parameters are sent to the DSP control board by serial transmission. The voltage loop feedback control is realized with Pulse Width Modulation, abbreviated PWM. The trigger delay of each power supply can be set independently, and the synchronicity of all power supplies work is achieved by parallel trigger. It can achieve the normal operation of DNB system by setting the output waveforms of all power supplies, the high voltage power supply trigger signal, the gas injection trigger signal and spectrometer trigger signal on the upper computer.Based on the structure of the DNB low voltage power supply, the MATLAB / SIMULINK simulation is used to compare the effects of different parameters of the filter elements on the output performance, for choosing the proper filter elements.The experimental test shows the DNB power supply system is well-performed; the output delay and ripple are improved; and the DNB power system operating parameters reach the demand of DNB system.