A microwave coherent backscattering experiment has been
carried out on
Mirabelle, a weakly ionized plasma device, with the objective of
measuring the
electron-density fluctuation level. The experiment is a preliminary
step in order
to prepare the detection system for a microwave stimulated-backscattering
experiment. The incident electromagnetic wave is focused in
front of a plane
grid, which excites ion acoustic or electron Bernstein waves and induces
fluctuations in the plasma. The backscattering signal is collected by the
launching circuit and detected by homodyne mixing. The typical ratio of the
scattered power to the incident power is about 10−12
and the relative density fluctuations is of the order of
δne/ne
≈10−3 against a background electron density
ne=(1–5)×109
cm−3. The backscattering measurement is also compared
with Langmuir-probe measurements, and gives good agreement with the
relative density fluctuations. The spectral width of the
backscattered signal has
also been studied, by taking into account effects due to the incident-wave
focusing and plasma-wave damping.
Quantifying erosion and retention of silicon carbide due to D plasma irradiation in a high-flux linear plasma device
