Langmuir probe diagnosis of hydrogen plasma induced by helicon-wave under low pressure

The current-voltage characteristic of hydrogen plasmas induced by helicon waves was measured in situ by a Langmuir probe under low pressure. According to Druyvesteyn method, raw data were fitted by an exponential transformation to a tangent hyperbolic function. Electron density, effective electron temperature and electron energy probability function(EEPF) were calculated from the fitted curves. The variation law of electron density, effective electron temperature and EEPF was analyzed in relation to different experimental parameters. The results demonstrate that RF power, gas pressure and controlled magnetic field have significant effects on state parameters of plasma. Electron density jumps with the increase of RF power because of the transition of mode, and it increases linearly with con