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Title: Xenon ion beam characterization in a helicon double layer thruster

Abstract

A current-free electric double layer is created in a helicon double layer thruster operating with xenon and compared to a recently developed theory. The Xe{sup +} ion beam formed by acceleration through the potential drop of the double layer is characterized radially using an electrostatic ion energy analyzer. For operating conditions of 500 W rf power, 0.07 mTorr gas pressure, and a maximum magnetic field of 125 G, the measured beam velocity is about 6 km s{sup -1}, the beam area is about 150 cm{sup 2}, and the measured beam divergence is less than 6 deg.

Authors:
; ;  [1]
  1. Space Plasma, Power, and Propulsion Group, Research School of Physical Sciences and Engineering, Australian National University, Australian Capital Territory 0200 (Australia)
Publication Date:
OSTI Identifier:
20880193
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 89; Journal Issue: 26; Other Information: DOI: 10.1063/1.2426881; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAM-PLASMA SYSTEMS; ION BEAMS; LAYERS; MAGNETIC FIELDS; PLASMA ACCELERATION; PLASMA DIAGNOSTICS; PLASMA GUNS; PLASMA SHEATH; THRUSTERS; XENON; XENON IONS

Citation Formats

Charles, C., Boswell, R. W., and Lieberman, M. A. Xenon ion beam characterization in a helicon double layer thruster. United States: N. p., 2006. Web. doi:10.1063/1.2426881.
Charles, C., Boswell, R. W., & Lieberman, M. A. Xenon ion beam characterization in a helicon double layer thruster. United States. doi:10.1063/1.2426881.
Charles, C., Boswell, R. W., and Lieberman, M. A. Mon . "Xenon ion beam characterization in a helicon double layer thruster". United States. doi:10.1063/1.2426881.
@article{osti_20880193,
title = {Xenon ion beam characterization in a helicon double layer thruster},
author = {Charles, C. and Boswell, R. W. and Lieberman, M. A.},
abstractNote = {A current-free electric double layer is created in a helicon double layer thruster operating with xenon and compared to a recently developed theory. The Xe{sup +} ion beam formed by acceleration through the potential drop of the double layer is characterized radially using an electrostatic ion energy analyzer. For operating conditions of 500 W rf power, 0.07 mTorr gas pressure, and a maximum magnetic field of 125 G, the measured beam velocity is about 6 km s{sup -1}, the beam area is about 150 cm{sup 2}, and the measured beam divergence is less than 6 deg.},
doi = {10.1063/1.2426881},
journal = {Applied Physics Letters},
number = 26,
volume = 89,
place = {United States},
year = {Mon Dec 25 00:00:00 EST 2006},
month = {Mon Dec 25 00:00:00 EST 2006}
}
  • An ion beam generated by an annular double layer has been measured in a helicon thruster, which sustains a magnetised low-pressure (5.0 × 10{sup −4} Torr) argon plasma at a constant radio-frequency (13.56 MHz) power of 300 W. After the ion beam exits the annular structure, it merges into a solid centrally peaked structure in the diffusion chamber. As the annular ion beam moves towards the inner region in the diffusion chamber, a reversed-cone plasma wake (with a half opening angle of about 30°) is formed. This process is verified by measuring both the radial and axial distributions of the beam potential and beammore » current. The beam potential changes from a two-peak radial profile (maximum value ∼ 30 V, minimum value ∼ 22.5 V) to a flat (∼28 V) along the axial direction; similarly, the beam current changes from a two-peak to one-peak radial profile and the maximum value decreases by half. The inward cross-magnetic-field motion of the beam ions is caused by a divergent electric field in the source. Cross-field diffusion of electrons is also observed in the inner plume and is determined as being of non-ambipolar origin.« less
  • The ion beam generated by a helicon double layer has been electrically steered up to 20 deg. off axis by using a solenoid placed normal to the two axial solenoids of the helicon plasma source without significantly changing the beam exhaust velocity.
  • Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.
  • Electron energy probability functions (EEPFs) are measured across the radius (0{<=}r<6.85 cm) of a low pressure (0.3 mTorr) helicon plasma source terminated by a current-free double layer. The source field of about 130 G is generated using a Helmholtz coil pair and the radio frequency (rf) power is maintained at 250 W. All EEPFs exhibit a distribution with a temperature T{sub ebulk} out to a break energy {epsilon}{sub break} and a relatively depleted distribution for higher energies with a lower temperature T{sub etail}. T{sub ebulk} and T{sub etail} are about 8 eV and 5 eV, respectively, for r<4 cm andmore » increase up to about 14 eV and 9 eV near the source wall, i.e., near the rf antenna. {epsilon}{sub break} is found to correspond to the potential drop of the double layer for the central part of the source and to the sheath potential near the wall.« less
  • No abstract prepared.