CAREER: Development and Application of Compact Helicon Sources

University Of Maryland, College Park, College Park MD

Investigators

Abstract

0846320 Sedwick This research aims at developing key science to improve helicon radio-frequency (RF) plasma generation used for propulsion or semiconductor manufacturing. Its key hypothesis is that fields of permanent magnets can be shaped optimally through the application of the Meissner effect of superconductors. If successful, the results of the research will provide a unique capability for study and implementation of a compact, high-efficiency, and high-density source for RF plasmas. These plasmas are of significant commercial interest because of their unusually high ionization efficiency - typically an order of magnitude higher or more than other capacitively or inductively coupled RF plasmas. However, making helicon sources compact and efficient is difficult because of the need for an axial magnetic field to establish helicon wave propagation. Stronger fields provide higher densities, but the power required to maintain the field offsets the gains in ionization efficiency. For the case of propulsion, such sources could make possible the use of water or ammonia as a propellant, providing compact storage, ease of ground handling, and high propulsive efficiency while still providing high specific impulse. For semiconductor processing, the high-density plasmas can be formed from chemical etchants (such as sulfur hexafluoride) to accelerate the deep reactive-ion etching (DRIE) process in harder materials such as silicon carbide. The ability to shape and control these magnetic fields in a compact geometry also provides a unique capability for design of laboratory experiments that will allow study of the effects of field geometry (specified axial gradients, periodic and non-periodic perturbations) on, for example: 1) wave reflection/transmission, 2) absorption of RF power and 3) plasma acceleration. Another research element afforded by the inductive nature of the RF coupling that will be investigated as a result of this capability is the formation of plasmas using non-noble gases. Specifically of interest is the non-equilibrium composition of partially dissociated polyatomic molecules, and how they could be optimized or otherwise impacted under variations of the discharge parameters. Educational broader impacts of the research will include: 1) an expansion of undergraduate and graduate student research experiences in this field; 2) the development of course material that integrates the proposed research into a specialized graduate elective and a component of the undergraduate curriculum; 3) the development of international research experiences for undergraduates (IREUs) that will start with colleagues at the Australian National University and 4) development of outreach programs for high school students designed to excite and intrigue that age group. Plasmas can be mesmerizing, and are also a component of many modern high-definition televisions, something to which all high-school students can relate. The hardware used in the proposed research is uniquely well suited for development of a number of laboratory demonstrations designed to promote active learning. These demonstrations will include taking a substance through all four states of matter, introducing atomic structure through a substance's spectral radiation and demonstrating the magnetic shielding properties of a superconductor.