Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session PW1: Optical Diagnostics II |
Hide Abstracts |
Chair: Akihiro Kono, Nagoya University Room: Saratoga Hilton Ballroom 1 |
Wednesday, October 21, 2009 1:30PM - 1:45PM |
PW1.00001: Plasma diagnostic over prominent oxygen triplets Vladimir Milosavljevic, Albert R. Ellingboe, Stephen Daniels The plasma chemistry of fluorocarbon--oxygen--argon discharges and its influence on prominent oxygen triplets are presented. We investigate a cascade dependence of energy levels of the three oxygen triplets to the 777 oxygen triplet. The 777 triplet is very important for the measurement of atomic oxygen in low pressure plasmas, since the 777.417 nm spectral line is frequently used for actinometry. A carbon rich emission spectrum also has an influence on emission of the oxygen triplet spectral lines by including new lines, as well changing the spectral line shapes of existing oxygen lines. There is a link between emission of a couple atomic carbon lines (around wavelength 601 nm) and the oxygen spectral lines from 777 triplets. The experiments were performed in an Radio Frequency (RF) dual--frequency discharge chamber from Lam Research ``EXELAN$^{\textregistered}$,'' with drive frequencies 2MHz and 27MHz. Working gases are Ar--O$_2$--C$_4$F$_8$ mixtures, the total pressure was varied from 2 to 6 Pa. The RF powers of the lower frequency generator were varied from 0 to 600 W, and for the higher frequency generator the power was varied from 0 to 1200 W. Optical observations were carried out using a high resolution spectrometer with an ICCD camera and a low resolution spectrometer. [Preview Abstract] |
Wednesday, October 21, 2009 1:45PM - 2:00PM |
PW1.00002: Determination of escape factors for the 811.53 nm argon atomic line Christian Scharwitz, Toshiaki Makabe As discussed in a previous study [Appl. Phys. Lett. 92 (2008), 071501] it is of interest for the determination of the density of low-energy electrons in Ar-plasmas to perform optical emission spectroscopy (OES) on the atomic transition line of Ar(2p9) to Ar(1s5) at 811.53 nm. For the metastable level Ar(1s5) a high population density is expected and radiation trapping is a challenge for these measurements. Radiation trapping is typically treated with so-called escape factors. To evaluate escape factors for the 811.53 nm Ar line, in our recent work two measurement methods are applied to inductively coupled plasmas. Based on the technique by [J. Phys. D 41 (2008), 065206] one of the methods is developed in such a way that the radiation trapping will have no impact, the other method is affected by the radiation trapping. The analysis of the results of both methods is used to evaluate the escape factors. The obtained escape factors will be presented and the results help to enhance the analysis of the OES measurements. This work is supported by a Grant-in-Aid for the Global COE Program operated at Keio University from MEXT Japan. [Preview Abstract] |
Wednesday, October 21, 2009 2:00PM - 2:15PM |
PW1.00003: Color Schlieren Imaging for Plasma Diagnostics Arlen Ward, Il Gyo Koo, Zeng-Qi Yu, George Collins The value of color schlieren imaging is demonstrated for thermal analysis and fluid dynamics of plasmas in liquid and atmospheric environments. Temperature and density changes of the fluids allow for dynamic visualization of the plasma plume during the interactions. Video Schlieren techniques will be presented to compare and contrast the impact of plasma application to tissue proxy gels in both environments. [Preview Abstract] |
Wednesday, October 21, 2009 2:15PM - 2:45PM |
PW1.00004: Using C-R models to determine electron density and temperature in discharges containing rare gases Invited Speaker: Electron density $n_{e}$ and electron temperature $T_{e}$ are important parameters for describing the plasma discharges. In many cases, the rare gases are used as a feed gas or added as a trace gas in low-temperature discharges. The intensity ratio of their optical emissions can be used to determine these parameters nonintrusively by using simple collisional--radiative models (C-R model) describing the kinetics of the excited levels. In this presentation, some simple C-R models for optical diagnostics are reviewed. Kinetic regimes, with different dominant processes, are identified for the Paschen 2p, 3p, 4p and 5p levels. One can then select proper excited levels to determine the plasma parameters according to the operation conditions. For example, for a low-pressure Ar/Xe inductive discharge, the 2p$_{1}$ and 2p$_{5}$ levels of Ar and Xe are in the corona regime, with the electron impact excitation from the ground state being dominant. Rate of this process is sensitive to the electron energy. As a result, line-ratios of Ar and Xe are used to give $T_{e}$. To obtain $n_{e}$, line-ratios of argon 3p, 4p and 5p levels are used, due to the significant electron impact transfer processes on these levels. This technique has been applied for a capacitive discharge containing Ar/Xe/CF$_{4. }$Similar method can be used for atmospheric-pressure nonequilibrium discharges to obtain the electron density. For example, for an argon microwave microplasma, the 2p$_{1}$, 2p$_{3}$ and 2p$_{6}$ levels are found to be in the high-pressure nonequilibrium regime, with both the electron-impact and atom-collision processes being important. This provides a strong dependence of the line-ration on of $n_{e}$ . $T_{e}$ and $n_{e}$ obtained from this technique are compared with that from other methods, such as the Langmuir probe and the Stark broadening method. Satisfactory agreement is obtained. The uncertainties and limitations of the line-ratio technique are also discussed. [Preview Abstract] |
Wednesday, October 21, 2009 2:45PM - 3:00PM |
PW1.00005: Validation of Atomic Data Using a Plasma Discharge Dirk Dodt, Andreas Dinklage, Klaus Bartschat, Oleg Zatsarinny Using a neon discharge as a well-assessed reference, we demonstrate how such an arrangement can be employed to validate atomic data for discharge modeling. Specifically, a collisional-radiative-model of a neon DC discharge was set up using a set of structure and collision data from a semirelativistic $B$-spline $R$-matrix calculation~[1], and the electron-energy distribution function of the plasma was determined from the spectroscopic measurement~[2]. Since the model covers almost the entire visible spectrum, considering a large number of emission lines and all collisional coupling mechanisms enabled us to thoroughly test the consistency of the modeled excited-state populations. Inconsistencies, which appear as correction factors for rate coefficients, were extracted by means of Bayesian probability theory. Despite its limitations, the sensitivity of the approach was sufficient to provide critical information about the collision data, especially in cases where standard cross-section measurements using merged electron and atom beams are difficult to perform. The present approach thus complements experimental techniques to test theoretical predictions. [1] O.~Zatsarinny and K. Bartschat, J. Phys. B~{\bf 37}, 2173 (2004). [2] D.~Dodt {\it et al.}, J. Phys. D~{\bf 41}, 205207 (2008). [Preview Abstract] |
Wednesday, October 21, 2009 3:00PM - 3:15PM |
PW1.00006: Optical plasma diagnostics: understanding the Ar emission spectrum John B. Boffard, R.O. Jung, Chun C. Lin, A.E. Wendt Optical emission spectroscopy (OES) provides a simple, non-invasive method of learning about many important plasma parameters (e.g. electron temperature, number densities). Measurements of Ar spectra in the 350-1200 nm wavelength range made on an inductive coupled plasma system under a range of operating conditions are compared to calculated emission spectra based on a radiation model that combines an electron energy distribution function (eedf) and number densities of ground state and Ar($3p^54s$) atoms with experimentally measured electron-impact excitation cross sections. Comparisons of the experimental and calculated spectra provide a quantitative assessment of the role of many processes in shaping the emission spectrum and thereby demonstrate how OES results can be utilized to extract plasma parameters. Examples include using radiation trapping of the $1s_x-2p_y$ emission array to measure metastable densities which are compared to white-light absorption measurements; using electron-induced collisional de-excitation of the $5p_5$ level to measure electron density; and using variations in cross sections for excitation from the ground and metastable levels into $3p_x$ levels to obtain information on the electron temperature and shape of the eedf. [Preview Abstract] |
Wednesday, October 21, 2009 3:15PM - 3:30PM |
PW1.00007: Plasma diagnostics by optical emission spectroscopy on argon and comparison to Thomson scattering D.L. Crintea, U. Czarnetzki, S. Iordanova, I. Koleva, D. Luggenh\"olscher A novel optical emission spectroscopy (OES) technique for the determination of electron temperatures and densities in low-pressure argon discharges is compared to Thomson scattering (TS). The emission spectroscopy technique is based on the measurement of certain line ratios in argon and a collisional-radiative model (CRM) including metastable transport. The investigations are carried out in a planar inductively coupled neutral loop discharge over a wide range of pressures, $p$ = 0.05 Pa -- 5 Pa. The discharge is operated in pure argon at a frequency of $f$ = 13.56 MHz and powers varied between $P =$ 1 kW and 2 kW. Both diagnostics, OES and TS, are applied in parallel. Electron densities and temperatures obtained by both diagnostic techniques are compared. Further, absolute numbers of the metastable densities are derived. Excellent agreement is found throughout if depletion of the neutral gas density by increase of the gas temperature and electron pressure is included in the CRM. Electron pressure is the dominant depletion mechanism at gas pressures $p \le $ 0.1 Pa and rf powers $P >$ 1 kW. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700