Characterization of inductively coupled plasma generated by a quadruple antenna

The results of the characterization of large-scale RF plasma for studying nonlinear interaction with a high-power (∼400 MW) short duration (∼0.8 ns) microwave (∼10 GHz) beam are presented. The plasma was generated inside a Pyrex tube 80 cm in length and 25 cm in diameter filled by either Ar or He gas at a pressure in the range 1.3-13 Pa using a 2 MHz RF generator with a matching system and a quadruple antenna. Good matching was obtained between the plasma parameters, which were determined using different methods including a movable Langmuir probe, microwave cut-off, interferometry, and optical emission spectroscopy. It was shown that, depending on the gas pressure and RF power delivered to the antenna, the plasma density and electron temperature can be controlled in the range 1 × 1010-5 × 1012 cm−3 and 1-3.5 eV, respectively. The plasma density was found to be uniform in terms of axial (∼60 cm) and radial (∼10 cm) dimensions. Further, it was also shown that the application of the quadruple antenna, with resonating capacitors inserted in its arms, decreases the capacitive coupling of the antenna and the plasma as well as the RF power loss along the antenna. These features make this plasma source suitable for microwave plasma wake field experiments.