Comment on "Ion velocity analysis of rotating structures in a magnetic linear plasma device" [Phys. Plasmas 25, 061203 (2018)]

International audienceIn a recent paper (Phys. Plasmas 25, 061203, 2018), the authors have incorrectly analyzed the electric ion drift velocity experienced by heavy ions created in a plasma submitted to a low magnetic field. The authors have not taken into account that the cylindrical geometry induces a slow electric drift of the ions. Moreover, the low magnetization of the ions induces a large Larmor radius often larger than the diameter of the plasma column. The movement of the ions immediately after their creation is parallel to the local electric field and most often the ions are neutralized before experiencing the electric drift calculated along the classical guiding center theory. This has not been taken into account by the authors so that the analysis of the Laser Induced Fluorescence measurements presented in this paper is clearly invalid