Most changes are CCP to ICP which is a big change in density and efficiency; changes of ICP to Helicon may change the lower pressure limit or density at very low pressure. I have made an ICP/Helicon with very low rf voltage in the plasma (see my us inventions) iF IT IS A LOOP, mode M=0 How do you determine which mode , after the plasma density is created? It very well may start as Helicon and then switch to ICP. Said in a different way, what is the difference of an ICP in a magnetic field, where the plasma current density falls off linearly and a Helicon loop?