Calibration of a VUV spectrograph by collisional-radiative modelling of a discharge plasma (original) (raw)
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Validation of atomic data using a plasma discharge
New Journal of Physics, 2010
Using a neon discharge as a well-assessed reference, we demonstrate the validation of atomic data for discharge modeling with data from emission spectroscopy. 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 by Zatsarinny and Bartschat (2004 J. Phys. B: At. Mol. Opt. Phys. 37 2173) and the electron-energy distribution function of the plasma was determined from the spectroscopic measurement by Dodt et al (2008 J. Phys. D: Appl. Phys. 41 205207). Since the model covers almost the entire visible spectrum, considering a large number of emission lines and many important collisional coupling mechanisms, it enables us to thoroughly test the consistency of the modeled excited-state populations. Inconsistencies, which appear as correction factors for the rate coefficients, are 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 existing experimental techniques to test theoretical predictions.
An elegant method to estimate helium-like ion densities from visible and VUV plasma spectroscopy
A method is presented to estimate the densities of He-like carbon and oxygen ions from the observation of the Li-like 3p + 3s transitions inthe visible and the 3p + 2s transitions in the vacuum ulbaviolet The method is based on a zerodimensional model for plasmas with short particle confinement times. General coefficients for this study are derived and evaluated numerically. The method is applied to Extrap-T1 reversed field pinch data Cochrane D M and McWhirter R W P 1983 Phys. Scr. 28 25 Fonck R 1, Ramsey A T and Yelle R V 1982 Appl. Opr. 21 21 15 Fussmann G. Field A R. Kallenbach A, Krieger K, Steuer K-H and the ASDEX-Team 1991 P l a s m Phys. Conrml. Johnson L C and Hinnov E 1913 3. Qmnr. Specrrosc. Radinr. Trans. 13 333 Klose J Z and Wiese W L 1989 3. Quont. Specrnw. Radiai Tram. 42 331 Lang J and Summers H P private communication Spitzer L Jr 1962 Physics of Fully Ionized Cares 2nd edn (New York Wiley Interscience) p 136ff Sprott 1 C 1988 Phys. Fluids 31 2266 Summers H P 1914 Moa Nor. R. Asiron. Soc. 169 663 Zhang H L, Sompson D H and Fontes C J 1990 AI. D m Nucl. D m Tables 44 31 Fusion 33 1611
AIP Conference Proceedings
High sensitivity absorption spectroscopy involves the use of modem diode and CCD (charge coupled device) detector arrays to observe fractional absorptions of ultraviolet (UV) and vacuum ultraviolet (VUV) radiation as small as 0.00001. Stable arc lamps provide a continuum in some experiments, but experiments at very high spectral resolution or at VUV wavelengths require the greater spectral radiance of a synchrotron. Absolute densities of excited atoms, atomic ions, and molecular radicals are measured in both processing and lighting plasmas. Basic spectroscopic data needed for the analysis of astrophysical observations from the Hubble Space Telescope are measured using absorption ofFe+ in a hollow cathode discharge.
Calculated Plasma Parameters and Excitation Spectra of High-Pressure Helium Discharges
Plasma Chemistry and Plasma Processing, 1999
A collisional-radiative model was used to study the kinetics of an atmospheric pressure helium discharge. The electron kinetics was obtained from a two-term solution of the Boltzmann equation with electron–electron collisions included. The distribution of the helium electronic excited states was compared to measured values and used to calculate excitation temperatures. The results show that a unique value of the
In the present work an effort has been made to estimate the plasma parameters simultaneously like-electron density, electron temperature, ground state atom density, ground state ion density and metastable state density from the observed visible spectra of penning plasma discharge (PPD) source using least square fitting. The analysis is performed for the prominently observed neutral helium lines. The atomic data and analysis structure (ADAS) database is used to provide the required collisional-radiative (CR) photon emissivity coefficients (PECs) values under the optical thin plasma condition in the analysis. With this condition the estimated plasma temperature from the PPD is found rather high. It is seen that the inclusion of opacity in the observed spectral lines through PECs and addition of diffusion of neutrals and metastable state species in the CRmodel code analysis improves the electron temperature estimation in the simultaneous measurement.
Journal of Physics: Conference Series, 2015
Studies of spectrum emission from high density argon plasma corona has been done. The analysis of the boardening of spectral atomic lines of Ar-I profile has been curried out by using an empirical approximation based on a Voigt profile. Full-width at half-maximum (FWHM) of the spectral-lines of 763.5 nm has been determined from atmospheric pressure until liquid state. The study liquid argon was curried out in a variation of temperature from 87.5 K to 151.2 K and hydrostatics pressure from 2.1 MPa to 6.4 MPa. These pressure gives the densities N ∞ (i.e. density very far from ionization zone) a variation from 1.08 10 22 to 2.11 10 22 cm -3 . FWHM of Voigt approximation (W v ) of the line 763,5 nm of 'Ar I for: the emission lamp very low pressure (W v = 0,160 nm) and our corona discharge at a pressure of 3,5 MPa ( W v = 0,67 nm) and at a pressure of 9,5 MPa (W v = 1,16 nm). In gas, corona plasma has been generated from 0.1 MPa to 9.5 MPa. We found that the broadening spectral line increase by increasing densities both for . the spectral-lines of 763.5 nm and 696.5 nm. We concluded that broadening of spectrum cause of Van der Waals force.
An elegant method to estimate helium-like ion densities from visible and VUV plasma
A method is presented to estimate the densities of He-like carbon and oxygen ions from the observation of the Li-like 3p + 3s transitions inthe visible and the 3p + 2s transitions in the vacuum ulbaviolet The method is based on a zerodimensional model for plasmas with short particle confinement times. General coefficients for this study are derived and evaluated numerically. The method is applied to Extrap-T1 reversed field pinch data Cochrane D M and McWhirter R W P 1983 Phys. Scr. 28 25 Fonck R 1, Ramsey A T and Yelle R V 1982 Appl. Opr. 21 21 15 Fussmann G. Field A R. Kallenbach A, Krieger K, Steuer K-H and the ASDEX-Team 1991 P l a s m Phys. Conrml. Johnson L C and Hinnov E 1913 3. Qmnr. Specrrosc. Radinr. Trans. 13 333 Klose J Z and Wiese W L 1989 3. Quont. Specrnw. Radiai Tram. 42 331 Lang J and Summers H P private communication Spitzer L Jr 1962 Physics of Fully Ionized Cares 2nd edn (New York Wiley Interscience) p 136ff Sprott 1 C 1988 Phys. Fluids 31 2266 Summers H P 1914 Moa Nor. R. Asiron. Soc. 169 663 Zhang H L, Sompson D H and Fontes C J 1990 AI. D m Nucl. D m Tables 44 31 Fusion 33 1611
Methods for spectroscopic measurement of electric field in atmospheric pressure helium discharges
European Physical Journal-applied Physics, 2017
A short overview of the emission spectroscopy methods for measuring the macroscopic electric field in high pressure discharges with helium is given. The occurrence of macroscopic electric field is a consequence of the space charge buildup. It is a common feature of discharge sheaths, streamer heads and double layers. The spectroscopic methods are based on polarization-dependent Stark splitting and shifting of atomic lines in the presence of a relatively strong electric field. For high pressure discharges Stark shifting of helium lines and their forbidden counterparts is used. The advantage of Stark methods is their ab initio basis which makes them independent on other plasma parameters. A different method for field measurement, based on the helium line ratio, can be applied in cases where the Stark method cannot be used.
The Astrophysical Journal, 2000
On 1999 May 9 the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) recorded spectra from a high-temperature region located in the solar corona above the west limb. These spectra contain lines from rather less-abundant elements in solar plasmas. In this paper we present identiÐcations of the high-temperature K) Ne, (T e º 3 ] 106 Na, Mg, Ar, K, Ca, Ti, Cr, Mn, Fe, Co, and Ni lines that were detected in the 500È1600 spectral range A of SUMER. In addition, accurate wavelength measurements have been obtained with uncertainties varying between 0.015 and 0.040
Physica, 1973
An intensity-calibration method has been developed which is specially suitable for the vacuum ultraviolet wavelength region. This method is based on a theoretical calculation of the emission cross section of noble-gas resonance lines, the upper levels being excited by electrons. By means of relative line-intensity measurements as a function of electron energy the quantum efficiency of the spectrometer can be determined absolutely if the optical (dipole) oscillator strength is known from theory or experiment. The measurements have been performed under a special angle, so that polarization effects did not influence the measured intensities. The method is an application of the Fano plot; the cascade contributions are included by certain theoretical considerations. With this method a vacuum ultraviolet spectrometer has been calibrated absolutely in the wavelength region 50-120nm. With help of this calibration we determined absolute emission cross sections of some ion lines (resulting from the excitation of noble-gas ion levels). These ion lines now provide a secondary calibration "standard".