Potential structures of low electron-temperature plasma

Space potential structures of a very low electron-temperature plasma (T-e similar or equal to 0.1 eV) have been measured by a Langmuir probe. High energy electrons pass through a coarse grid biased negatively from a source region into a diffusion region. Cold electrons are produced through an ionization by these high energy electrons in the diffusion region. When the space potential of the plasma in the diffusion region is increased by the target potential biased positively. A potential dip is formed in front of the target plate. The cold electrons are well confined by this potential dip.