Parametric Analysis And Optimization Of Diagnostic Neutral Beam Ion Source On J-TEXT

In the study of fusion plasma physics,ion temperature and rotation speed of plasma are important parameters to describe plasma characteristics.These parameters play a key role in plasma confinement,energy transport,momentum transport and impurity transport.Many diagnostic tools have been developed in order to obtain these parameters,and CXRS is considered to be one of the most effective techniques.J-TEXT laboratory is currently building a set of charge exchange recombination spectroscopy systems based on diagnostic neutral beam injection(DNB)to diagnose the plasma ion temperature profile and rotational velocity profile.Based on this system,the diagnostic capability of the J-TEXT Tokamak can be greatly improved.In this paper,the influence of discharge parameters on the working state of ion source is analyzed,and the beam parameters are measured based on the spectral technique to lay the foundation for the stable operation of the DNB system.The ion source of the J-TEXT DNB system is a hot cathode ion source.The work parameters(discharge pressure,filament voltage and arc voltage)of the ion source will affect the plasma density and electron temperature,thus affecting the arc current intensity and ionization products,and then decide the neutral beam intensity and the ratio of different beam energy component.The higher the discharge pressure,the higher the filament voltage and the higher the arc voltage,the greater the arc current can be obtained.However,the increase of discharge pressure causes a reduction in the electron temperature.By adjusting the operating parameters of the ion source,the arc current was carried out and the electronic temperature was measured by double-line method.The parameters of the ion source operating parameters were obtained: discharge pressure 0.27 Pa,filament voltage 11 V,no-load arc pressure 250 V.In order to further analyze the working state of the ion source,a multi-channel Doppler frequency shift spectroscopy(DFSS)system is constructed.DFSS system can measure three diagnostic neutral beam parameters simultaneously including the beam energy fractions by Doppler frequency shift,intensity distributions by extrapolation method,and divergences by 1/e line broadening and geometric method.Under the 24 kV acceleration voltage,the preliminary results obtained are as follows: the ratio of the H(E)is about 10%,the beam diameter is about 8.1 cm at a distance of 2 m from the accelerator,and beam divergence angle is about 3.3 degrees.The experimental results show that the DFSS system can meet the requirements of real-time detection of neutral beam quality,and provide a reference for CXRS analysis.