Variable frequency matching to a radiofrequency source immersed in vacuum

A low-weight (0.12 kg) low-volume fixed ceramic capacitor impedance matching system is developed for frequency agile tuning of a radiofrequency (rf) Helicon plasma thruster. Three fixed groups of capacitors are directly mounted onto a two loop rf antenna with the thruster immersed in a vacuum chamber. Optimum plasma tuning at the resonance frequency is demonstrated via measurements of the load impedance, power transfer efficiency and plasma density versus driving frequency in the 12.882–14.238 MHz range. The resonance frequency with the plasma on is higher than the resonance frequency in vacuum. The minimum rf power necessary for ignition decreases when the ignition frequency is shifted downwards from the resonance frequency. This development has direct applications in space qualification and space use of rf plasma thrusters.

[1]  A. Gallimore,et al.  Performance and Probe Measurements of a Radio-Frequency Plasma Thruster , 2013 .

[2]  C. Charles,et al.  Approaching the theoretical limit of diamagnetic-induced momentum in a rapidly diverging magnetic nozzle. , 2013, Physical review letters.

[3]  M. Walker,et al.  Thrust Measurements of a Radio Frequency Plasma Source , 2013 .

[4]  S. Pottinger,et al.  Helicon double layer thruster operation in a low magnetic field mode , 2012 .

[5]  Kazunori Takahashi.  Radiofrequency antenna for suppression of parasitic discharges in a helicon plasma thruster experiment. , 2012, The Review of scientific instruments.

[6]  C. Charles,et al.  Axial force imparted by a current-free magnetically expanding plasma , 2012 .

[7]  J. Byun,et al.  Atmospheric-pressure plasma sources for biomedical applications , 2012 .

[8]  Christine Charles,et al.  Measurement and modelling of a radiofrequency micro-thruster , 2012 .

[9]  C. Charles,et al.  A magnetic nozzle calculation of the force on a plasma , 2012 .

[10]  C. Charles,et al.  Electron diamagnetic effect on axial force in an expanding plasma: experiments and theory. , 2011, Physical review letters.

[11]  V. Godyak.  Electrical and plasma parameters of ICP with high coupling efficiency , 2010 .

[12]  M. Walker,et al.  rf power system for thrust measurements of a helicon plasma source. , 2010, The Review of scientific instruments.

[13]  C. Charles,et al.  Operating Radio Frequency Antennas Immersed in Vacuum: Implications for Ground-Testing Plasma Thrusters , 2010 .

[14]  C. Charles,et al.  High density mode in xenon produced by a Helicon Double Layer Thruster , 2009 .

[15]  T. Fujiwara,et al.  Observation of weakly and strongly diverging ion beams in a magnetically expanding plasma , 2009 .

[16]  D. Goebel,et al.  Analytical Discharge Model for RF Ion Thrusters , 2008, IEEE Transactions on Plasma Science.

[17]  J. Foster,et al.  A Magnetically Enhanced Inductive Discharge Chamber for Electric Propulsion Applications , 2008, IEEE Transactions on Plasma Science.

[18]  Christine Charles,et al.  Xenon ion beam characterization in a helicon double layer thruster , 2006 .

[19]  Kyoichiro Toki,et al.  Small helicon plasma source for electric propulsion , 2006 .

[20]  Kurt A. Polzin,et al.  Faraday acceleration with radio-frequency assisted discharge , 2006 .

[21]  Henry Oman,et al.  Fundamentals of Electric Propulsion , 2006 .

[22]  C. Charles,et al.  Experimental evidence of a double layer in a large volume helicon reactor. , 2005, Physical review letters.

[23]  M. Lieberman,et al.  Energy balance in a low pressure capacitive discharge driven by a double-saddle antenna , 2003 .

[24]  Alvy Ray Smith.  Digital Humans Wait in the Wings. , 2000 .

[25]  Francis F. Chen,et al.  Helicons-the early years , 1997 .

[26]  Uwe R. Kortshagen,et al.  On the E - H mode transition in RF inductive discharges , 1996 .

[27]  C. Charles,et al.  Breakdown, steady‐state, and decay regimes in pulsed oxygen helicon diffusion plasmas , 1995 .

[28]  C. Charles,et al.  Effect of wall charging on an oxygen plasma created in a helicon diffusion reactor used for silica deposition , 1995 .

[29]  Benjamin Alexandrovich,et al.  A simple analysis of an inductive RF discharge , 1992 .