Optical, wave measurements, and modeling of helicon plasmas for a wide range of magnetic fields

Abstract

Helicon waves are excited in a plasma wave facility by a half-turn double-helix antenna operating at 13.56 MHz for static magnetic fields ranging from 200 to 1000 G. A non-perturbing optical probe located outside the Pyrex™ plasma chamber is used to observe 443 nm Ar II emission that is spatially and temporally correlated with the helicon wave. The Ar II emission is measured along with wave magnetic and Langmuir probe density measurements at various axial and radial positions. 105 GHz interferometry is used to verify the bulk temperature corrected Langmuir probe measurements. The measured peak Ar II emission phase velocity is compared to the measured wave magnetic field phase velocity and code predicted wave phase velocity for the transition and blue mode regimes. Very different properties of the optical emission peak phase and wave characteristics for the transition and helicon modes of operation are observed. Comparison of the experimental results with the ANTENAII code ͓Y. Mouzouris and J. E. Scharer, IEEE Trans. Plasma Sci. 24, 152 ͑1996͔͒ is carried out for the wave field measurements for the two regimes of operation.

Plasma dynamics in a helicon thruster

“…Values of n eS /n 0 = O(10 −2 ) have been observed by Tysk et al [25]. The main result from the inertial layer is the determination of the electron azimuthal energy.…”

Helicon mode formation and radio frequency power deposition in a helicon-produced plasma

“…[2][3][4] Collisionless resonant electron heating may produce hot electrons in the electron energy distribution function. Though, this mechanism may occur at low external magnetic field ͑B 0 Յ 10 mT͒ and low plasma density ͑n e Յ 10 18 m −3 ͒, 5 whereas, probably due to the high collisionality, it is unlikely to play a role in high-density helicon plasma operating in the blue mode. Indeed, in recent investigations on such a plasma, we found no evidence for significant interaction between resonant electrons and helicon waves.…”

Magnetic confinement of a high-density cylindrical plasma

“…This illustrates the excellent confinement provided by the applied magnetic field; for instance, experimental measurements by Tysk et al 17 yield n eS =n 0 $ 1%. Equation (13) has to be compared with n eS n 0 ¼ e À1=2 ' 0:61;…”