High-energy electron-free plasma source

A capacitively coupled 13.56‐MHz radio‐frequency (rf) plasma is produced in the presence of a magnetic ring‐cusp field. In order to determine an accurate electron energy distribution function (EEDF) and an electron density by means of Langmuir probe in this rf plasma, an asymmetrical double probe was used. The measured EEDF showed the Maxwellian‐like distribution from a drift motion in the magnetic ring‐cusp field. Furthermore, it is seen that this rf plasma is favorable for excluding high‐energy electrons. The electron density for helium (He) is proportional to the rf power, being equal to 2×1010 cm−3 at 400 W.