Enhanced diamagnetic perturbations and electric currents observed downstream of the high power helicon

Journal Article · Sun May 15 00:00:00 EDT 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3574753· OSTI ID:21537836

Roberson, B Race; Winglee, Robert; Prager, James ^[1]

---

1. Department of Earth and Space Sciences, University of Washington, Johnson Hall 070, Box 351310, 4000 15th Avenue NE, Seattle, Washington 98195-1310 (United States)

The high power helicon (HPH) is capable of producing a high density plasma (10{sup 17}-10{sup 18} m{sup -3}) and directed ion energies greater than 20 eV that continue to increase tens of centimeters downstream of the thruster. In order to understand the coupling mechanism between the helicon antenna and the plasma outside the immediate source region, measurements were made in the plasma plume downstream from the thruster of the propagating wave magnetic field and the perturbation of the axial bulk field using a type 'R' helicon antenna. This magnetic field perturbation ({Delta}B) peaks at more than 15 G in strength downstream of the plasma source, and is 3-5 times larger than those previously reported from HPH. Taking the curl of this measured magnetic perturbation and assuming azimuthal symmetry suggests that this magnetic field is generated by a (predominantly) azimuthal current ring with a current density on the order of tens of kA m{sup -2}. At this current density the diamagnetic field is intense enough to cancel out the B{sub 0} axial magnetic field near the source region. The presence of the diamagnetic current is important as it demonstrates modification of the vacuum fields well beyond the source region and signifies the presence of a high density, collimated plasma stream. This diamagnetic current also modifies the propagation of the helicon wave, which facilitates a better understanding of coupling between the helicon wave and the resultant plasma acceleration.

• OSTI ID: 21537836
• Journal Information: Physics of Plasmas, Vol. 18, Issue 5; Other Information: DOI: 10.1063/1.3574753; (c) 2011 American Institute of Physics; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANTENNAS
COUPLING
CURRENT DENSITY
DISTURBANCES
ELECTRIC CURRENTS
HELICON WAVES
MAGNETIC FIELDS
PLASMA ACCELERATION
PLASMA DENSITY
PLASMA DIAMAGNETISM
WAVE PROPAGATION
ACCELERATION
CURRENTS
DIAMAGNETISM
ELECTRICAL EQUIPMENT
ELECTROMAGNETIC RADIATION
EQUIPMENT
MAGNETISM
RADIATIONS