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SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Air Force Research Laboratory (AFMC) AFRL/PRS
SPONSOR/MONITOR'S
Pollux Drive
NUMBER(S)Edwards AFB CA 93524-7048 AFRL-PR-ED-TP-2007-388
DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited (PA #07323A).
SUPPLEMENTARY NOTESFor presentation at the 30 th International Electric Propulsion Conference (2007 IEPC), Florence Italy, 17-20 Sep 2007. IEPC-2007 14. ABSTRACT The requirement for a highly efficient plasma source that can operate in an electric propulsion capacity has led to renewed research on helicons. Helicons have long been known to be a highly efficient (>90%) and high density (>1013 cm-3) method to generate plasma. It has not been until recently though, that these sources have been given interest by the propulsion community. Much recent research toward this end has focused on detachment of ions from the magnetic field lines which can be as great as a few hundred Gauss. Investigations to date have shown that this may be possible through ambipolar effects or acceleration through a double layer. Preliminary investigations suggest electrons that are generated near the diverging section of the axial magnetic field will enhance the ambipolar acceleration of ions out of the device. Toward this end, a radio frequency (RF) antenna that propagates a wave toward the converging section of the device (diverging section of the magnetic field) will dictate where the bulk of the RF energy is absorbed. This has led to the design of a conical antenna. Preliminary work based on a uniform density model suggest that at smaller radii there is an increase in electron density and that there are further ways to control the density and temperature based on considerations such as pressure, frequency, and antenna length. The focus of this investigation will be to observe and compare the differences in the wave fields (Br, Bθ, Bz) between a traditional cylindrical helicon and that of a conical helicon.
SUBJECT TERMS
AbstractThe requirement for a highly efficient plasma source that can operate in an electric propulsion capa...
