A microwave interferometer for steady-state plasma density measurements

Reconstruction of plasma density profiles by measuring spectra of radiation emitted from oscillating plasma dipoles

“…Furthermore, quantitative knowledge of the electron density, its fluctuation and profile type is required for developing fusion plasma devices [2][3][4][5][6][7][8][9][10] and for understanding laser-plasma interactions in general [11][12][13][14]. It is also necessary for characterising plasma-related instruments, including those used for material processing [15][16][17][18][19]. Many plasma diagnostics techniques currently exist; their operating principles depend on the plasma parameter regimes.…”

“…The most widely used and well-developed plasma diagnostics technique is interferometry, which exploits the change in phase that electromagnetic (EM) waves experience as they pass through media with variable refractive indices. By analysing the resulting interference fringes using mathematical inversion processes, such as the Abel inversion, the plasma density can be deduced [1,4,12,15,16]. However, the technique has limitations: the phase change is integrated along the path, and the local density cannot be determined at specific points along them unless particular symmetries are assumed.…”