The boundary conditions in an electron cyclotron resonance (ECR) source have been modified to mimic the operating conditions where current-free double-layers (DLs) have been recently measured in rf helicon plasmas. The plasma is heated or generated by the ECR at 875 G inside a dielectric source tube, and expands into a grounded diffusion chamber (terminated by a glass plate) by a rapidly decrea...

Recent developments in laboratory double layers from the late 1980s to the spring of 2007 are reviewed. The paper begins by a lead up to electric double layers in the laboratory. Then an overview of the main double layer devices and properties is presented with an emphasis on current-free double layers. Some of the double layer models and simulations are analysed before giving a more complete d...