An appraisal of the influence of a weak magnetic field to the estimation of plasma density by a cylindrical Langmuir probe

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:212857

Kudrna, P; Chudacek, O; Sicha, M; Tichy, M ^[1]

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1. Charles Univ., Prague (Czech Republic); and others

During the course of the study of the cylindrical magnetron discharge at the Greifswald University we used the cylindrical Langmuir probe for estimation of radial dependences of the plasma density and of the electron energy distribution function. Since the probe had to be operated in a magnetoplasma we attempted to assess experimentally the influence of the applied magnetic field on the plasma density determined by a cylindrical probe. The theoretical assessment of the effect of the magnetic field on the charged particle collection by a Langmuir probe has been treated by Rubinstein and Laframboise in assuming the cylindrical probe operating in a {open_quotes}large Debye length{close_quotes} (i.e. {lambda}{sub D}>>a{sub g}, {lambda}{sub D}=({epsilon}{sub 0}kT{sub e}/q{sub 0}{sup 2}n{sub e}){sup 1/2} is the Debye length, a{sub g}=({pi}m{sub e,i}kT{sub e,i}/2){sup 1/2}/(q{sub 0}B) is the electron/ion mean gyroradius, all the symbols have their usual meanings) collisionless plasma. The theory calculated a.o. the electron currents to a cylindrical Langmuir probe at the space potential with the result that this current is minimally influenced by the magnetic field when the axis of the cylindrical probe is positioned perpendicular to the magnetic field lines. This particular result is suitable for the assessment of the error introduced by the magnetic field to the plasma density estimation since the electron density can be estimated from the electron probe current at the space potential. The dependence of this error on the Debye length {lambda}{sub D} remains, however, unknown and has not been to our knowledge fully resolved even in newer works.

• OSTI ID: 212857
• Report Number(s): CONF-950749--
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
66 PHYSICS
COLLISIONLESS PLASMA
ELECTRON DENSITY
ELECTRONS
ENERGY SPECTRA
LANGMUIR PROBE
MAGNETIC FIELDS
MAGNETRONS
PLASMA DENSITY
PLASMA DIAGNOSTICS