66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013;
Princeton, New Jersey
Session TF1: Diagnostics II
10:30 AM–12:15 PM,
Friday, October 4, 2013
Room: Ballroom I
Chair: Azer Yalin, Colorado State University
Abstract ID: BAPS.2013.GEC.TF1.3
Abstract: TF1.00003 : Quantitative diagnostics of reactive, multicomponent low-temperature plasmas*
11:00 AM–11:30 AM
Preview Abstract
Abstract
Author:
Thomas Schwarz-Selinger
(Max-Planck Institut f\"{u}r Plasmaphysik, EURATOM Association, Germany)
The special emphasis in this work is put on the quantitative determination
of the plasma composition of an inductively coupled low temperature plasma
(ICP). Several standard plasma diagnostic techniques were applied. As a test
case for a multi-component low-temperature plasma argon-hydrogen as well as
argon-hydrogen-nitrogen mixed plasmas were investigated.
For steady-state plasma operation the ion density and electron temperature
were determined with a single tip Langmuir probe. A multi-grid miniature
retarding-field analyzer was used to measure the mass integrated ion flux.
An energy-dispersive mass spectrometer - a so-called plasma monitor (PM) -
was applied to sample ions from the plasma to derive the ion composition.
The degree of dissociation of hydrogen and the gas temperature were derived
from optical emission spectroscopy. The gas temperature was estimated by the
rotational distribution of the Q-branch lines of the hydrogen
Fulcher-$\alpha $ diagonal band for the argon-hydrogen mixed plasmas and
from the second positive system of N$_{2}$ in
argon-hydrogen-nitrogen mixed plasmas. The degree of dissociation of
hydrogen was measured by actinometry. The influence of the substrate
material of the counter electrode (stainless steel, copper, tungsten, Macor,
and aluminium) on the atomic hydrogen concentration was investigated by OES.
In addition, ionization-threshold mass spectrometry (ITMS) was used to
determine the densities of atomic nitrogen (N) and atomic hydrogen (H and
D). Pulsed plasma operation was applied to directly measure the loss rate of
H, D and N in the afterglow from the temporal decay of the ITMS signal. From
these data the wall loss probability of atomic hydrogen was determined.
Furthermore, a zero-dimensional rate equation model was devised to explain
the ion composition in these mixed plasmas with different admixture ratios.
In addition to the experimental data on electron density, gas temperature,
total pressure, atomic hydrogen density, and Ar, H$_{2}$, and
N$_{2}$ fraction, the chamber geometry and the required collisional
rate coefficients are input parameters for the model. The model was applied
to calculate the ion densities and the electron temperature and describes
the main features reasonably well supporting the validity of the plasma
diagnostics applied.
*In collaboration with Maik Sode and Wolfgang Jacob, Max-Planck Institut f\"{u}r Plasmaphysik, EURATOM Association, Germany.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.GEC.TF1.3