Byhring, H. S.Charles, C.Fredriksen, Å.Boswell, R. W.2015-12-062015-12-061070-664Xhttp://hdl.handle.net/1885/17028Ion energy measurements were taken simultaneously using one retarding field energy analyzer placed at the open end of the plasma source, and one in the plasma diffusion region of an expanding low pressure argon plasma. An electric double layer was found, which is well separated from the region of high magnetic field and which is downstream of the maximum in the magnetic field gradient. An axially movable analyzer was used to determine the position of the double layer. It appears to be more closely connected to the rapid change in diameter from the source to the diffusion chamber, but still has a radial dimension close to that of the source diameter. These results suggest that the double layer forms, not as much as a result of a magnetic nozzle, but rather as a reaction to a dramatic change in boundary conditions. Still, a magnetic field of at least a few tens of Gauss in the double layer region is necessary for its spontaneous formation.http://www.sherpa.ac.uk/romeo/issn/1070-664X..."Publishers version/PDF may be used on author's personal website, institutional website or institutional repository" from SHERPA/RoMEO site (as at 7/12/15). Copyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas and may be found at https://doi.org/10.1063/1.3002396Keywords: Argon; Boundary value problems; Diffusion; Digital signal processing; Inert gases; Magnetic field measurement; Magnetic fields; Plasmas; Rivers; Semiconductor doping; A magnetic fields; Argon plasmas; Diffusion chambers; Double layer regions; Double layer2008-10-3010.1063/1.30023962016-02-24