(where the helicon double-layer thruster and the Variable Specific Impulse Magnetoplasma Rocket both make use of helicons in their plasma heating phase). Helicons are also utilized in the procedure of plasma etching, used in the manufacture of computer microcircuits. A helicon discharge is an excitation of plasma by helicon waves induced through radio frequency heating. The difference between a helicon plasma source and an inductively coupled plasma (ICP) is the presence of a magnetic field directed along the axis of the antenna. The presence of this magnetic field creates a helicon mode of operation with higher ionization efficiency and greater electron density than a typical ICP. The Australian National University, in Canberra, Australia, is currently researching applications for this technology. A commercially developed magnetoplasmadynamic engine called VASIMR also uses helicon discharge for generation of plasma in its engine. Potentially, helicon double-layer thruster plasma-based rockets are suitable for interplanetary travel. See also Helicon double-layer thruster Variable Specific Impulse Magnetoplasma Rocket References Electromagnetic radiation