In this contribution, an innovative K-band (18-26.5 GHz) microwave polarimetric system is presented. The experimental setup for the detection of the magnetoplasma-induced Faraday rotation  is based on a precision rotating polarimetric system and on waveguide Orthomode Transducers (OMTs). In presence of a known longitudinal magnetic field component, (0.1 T in our case), the system is able to provide reliable line-integrated electron density measurements, in the range 1017-1019m-3. It is worth noting that any non-intrusive plasma electron density measurement in compact microwave-based Ion Sources is a challenge, especially due to the small size of the plasma chamber with respect to the required probing wavelength. The approach considered here overcomes many drawbacks: an analysis method has been developed on purpose in order to detect the polarization plane excluding the effects of the cavity resonator when a wire grid polarizer is placed inside the cavity itself. The measurement strategy and data analysis allow being sensitive even in the extreme unfavourable conditions Î»pâLpâLc, being Î»p, Lpand Lcthe probing signal wavelength, the plasma dimension and the plasma chamber length respectively. The developed noninvasive diagnostic method will represent a powerful tool for probing in a non-intrusive way very compact devices, such as plasma-based Electron Cyclotron Resonance Ion Sources and, more generally, compact magnetic traps containing microwave-generated plasmas. Finally, our measurements can be directly compared (and crosschecked) with the already developed Frequency-Modulated Continuous-Wave (FMCW) interferometer setup .
|Titolo:||Microwave polarimetric setup for plasma density measurement in compact Ion sources|
|Data di pubblicazione:||2017|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|