The First Measurement of Plasma Density in an ECRIS-like Device by Means of a Frequency-sweep Microwave Interferometer

The note presents the first plasma density measurements collected by a novel microwave interferometer in a compact Electron Cyclotron Resonance Ion Sources (ECRIS). The developed K-band (18.5 ÷ 26.5 GHz) microwave interferometry, based on the Frequency-Modulated Continuous-Wave method, has been able to discriminate the plasma signal from the spurious components due to the reflections at the plasma chamber walls, when working in the extreme unfavorable condition λ ≃ L ≃ L (λ, L, and L being the probing signal wavelength, the plasma dimension and the plasma chamber length, respectively). The note describes the experimental procedure when probing a high density plasma (n > 1 ⋅ 10 cm) produced by an ECRIS prototype operating at 3.75 GHz.