Berlin 2001 – scientific programme
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P: Plasmaphysik
P 11: Dusty Plasmas and Low Temperature Discharges (Poster Session)
P 11.17: Poster
Thursday, April 5, 2001, 12:30–15:00, AT2
Langmuir probe measurements in high pressure arcs — •Jens Luhmann1, Daniel Nandelstädt1, Jürgen Mentel1, and M. S. Benilov2 — 1Ruhr-University Bochum, Fundamentals of Electrical Engineering Group, Universitätsstr. 150, 44780 Bochum, Germany — 2Departamento de Física,
An arc discharge is operated in argon or xenon
at a pressure of 0.1-1MPa and a dc current of 1-10A. In order to
verify theoretical models for the plasma boundary layer in front
of cathodes the fall voltage of pure and modified tungsten
cathodes is investigated. Therefore two Langmuir probes are
inserted into the arc tube to determine the plasma potential on
the axis of the arc column at the position of the probe. The
probes are made of thin tungsten wires shaped as half circles at
their ends so that both probes form a ring which surrounds the
arc. One probe is operated at floating potential, the other is
connected with a voltage ramp generator which is biased against
the grounded cathode. From the recorded
current-voltage-characteristic the plasma potential on the axis is
deduced by theoretical consideration. To verify the results of the
probe measurements they are compared with those of caloric
measurements. The agreement of the results achieved by the
different methodes is remarkably good. It can be concluded, that
the cathode voltage fall is a function of the current, the arc
attachment, the gas, the cathode shape and material.
Financial support is supplied by the German Federal Ministry
of Education and Research (Ref.-No. 13N7763).