| CPC H01J 37/32935 (2013.01) [H01J 37/32926 (2013.01); G21B 1/05 (2013.01)] | 7 Claims |
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1. A diagnostic method for measuring potential and electric field of plasma, comprising:
(1) according to an operation parameter of a magnetic confinement fusion device, selecting a plurality of candidate particle elements, and obtaining relevant parameter data of the plurality of candidate particle elements; wherein the relevant parameter data comprises particle mass data, primary collision ionization cross section data and secondary collision ionization cross section data; the operation parameter comprises a background magnetic field of the magnetic confinement fusion device, an electron temperature of a plasma and an electron density of the plasma;
(2) based on the operation parameter and the relevant parameter data, calculating beam trajectories and effective electron-impact ionization cross-section data of the plurality of candidate particle elements, and calculating signal-noise ratios of the plurality of candidate particle elements based on the beam trajectories and the electron-impact ionization cross-section data; and according to the signal-noise ratios, selecting an appropriate element from the plurality of candidate particle elements as a neutral beam particle element for diagnosis;
(3) based on particle mass data of the neutral beam particle element, performing iterative calculation to obtain a preset parameter which enables the beam trajectories to pass through an entrance slit of an analyzer; wherein the preset parameter comprises incident energy, incident angle and sampling area;
(4) heating a solid-state thermionic source corresponding to the neutral beam particle element to generate ions, and accelerating the ions by utilizing Pierce electrode equipment to obtain a directed ion beam; subjecting the directed ion beam to exchange with a preset neutral gas charge to generate a neutral beam with a preset incident energy; and based on the preset parameter, injecting the neutral beam into the plasma at a preset incident angle; and
(5) analyzing and calculating, by the analyzer, a primary beam generated by collision ionization of the neutral beam in a first sampling area to obtain an energy of a primary beam; based on energy difference between the primary beam and the neutral beam, obtaining a potential of the first sampling area according to law of conservation of energy; and repeating the iterative calculation and changing the preset parameter, so as to collect an energy of a primary beam generated in a second sampling area, thereby obtaining potential spatial distribution of the plasma at different radial positions and a radial electric field; and finishing the diagnosis;
wherein the step of calculating the beam trajectories based on the operation parameter and the relevant parameter data comprises:
based on the particle mass data, injecting a neutral beam of one of the plurality of candidate particle elements into the plasma at a certain incident velocity and a certain incident angle to undergo collision ionization with electrons in the plasma to generate the primary beam; wherein the primary beam deflects and exits the plasma under the action of a background magnetic field; and each of the beam trajectories is calculated as follows:
 wherein r(t) represents a beam trajectory; d represents a differential sign; dr(t) represents a differential of r(t); t represents time; dt represents a differential of t, v0 represents an incident velocity of the neutral beam; m represents a particle mass of a corresponding candidate particle element; q represents the number of electric charges; for the neutral beam, q=0, and for the primary beam, q=e, wherein e represents the number of electric charges of an electron; B represents the background magnetic field; a particle movement velocity vb along the beam trajectory is represented as
 for neutral beams of other elements among the plurality of candidate particle elements, in the same beam trajectory, an incident velocity va′ is obtained according to the same Larmor radius through the following equation:
 wherein m′ represents particle mass of the other elements;
the step (2) is performed through steps of: calculating the effective electron-impact ionization cross-section data based on a Maxwell speed distribution function, the primary collision ionization cross section data and the secondary collision ionization cross section data through the following equation:
 wherein v represents a particle-electron relative velocity, and v=|vb−ve|, wherein, vb represents a particle movement velocity, and ve represents an electron movement velocity; d represents the differential sign; dv represents a differential of v; f(v) represents the Maxwell speed distribution function; Te represents the electron temperature of the plasma; me represents an electron mass; k represents a Boltzmann constant; σ(v) represents a collision ionization cross section; σeff represents an effective collision ionization cross section, wherein a primary effective collision ionization cross section σeff1 is obtained by substituting a primary collision ionization cross section σ1(v) into the above equation, and a secondary effective collision ionization cross section σeff2 is obtained by substituting a secondary collision ionization cross section σ2(v) into the above equation;
calculating the signal-noise ratios of the plurality of candidate particle elements according to the operation parameter, the relevant parameter data, the beam trajectories and the effective electron-impact ionization cross-section data through the following equation:
 wherein Id/I0 represents a signal-noise ratio; ne represents the electron density of the plasma; w represents a width of the entrance slit; d represents the differential sign; dl represents a differential of l; l represents the beam trajectory; ti represents a time that the neutral beam reaches a core of the plasma to undergo collision ionization to generate the primary beam; td represents a time that the primary beam exits the plasma; and σeff1 is the primary effective collision ionization cross section, and σeff2 is the secondary effective collision ionization cross section; and
according to the signal-noise ratios of the plurality of candidate particle elements, selecting an element with a signal-noise ratio higher than 10−3 as the neutral beam particle element for the diagnosis;
in the step (5), the potential is obtained through the following equation:
 wherein φi represents the potential of the first sampling area; Ed represents the energy of the primary beam; E0 represents the incident energy of the neutral beam; and e represents the number of electric charges of an electron.
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