A spatially resolved relaxation method for pLTE plasma diagnostics in free-burning arcs

Kühn, Gerrit; Kock, M.

doi:10.1088/0022-3727/39/11/014

Cited by 18 publications

(12 citation statements)

References 46 publications

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“…The finding was confirmed by an investigation of the electrode behaviour within the same type of lamps when they were operated with switched dc currents of different amplitudes and operation frequencies [15,16]. It was also confirmed when the same type of lamps was seeded with TmI 3 [17], CeI 3 or LaI 3 [18,19].…”

Section: Introductionmentioning

confidence: 73%

“…The discharge assumes the shape of a free burning arc within the vessel. An overview of the experimental setup is given in [3], figure 3, or in [4], figure 3.…”

Section: Experimental Investigations and Resultsmentioning

confidence: 99%

“…An account was given in several papers of a research group at the University of Hannover [1][2][3][4] of a special mode of constricted arc attachment on a thoriated tungsten cathode. Electrodes of this kind are used in high-intensity discharge (HID) lamps.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of the hot core mode of arc attachment at a thoriated tungsten cathode by an emitter spot model

Bergner

Scharf

Kühn

et al. 2014

Plasma Sources Sci. Technol.

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Recently, a constricted attachment of an atmospheric pressure low-current argon arc in the centre of the flat end face of a thoriated tungsten cathode was observed and spectroscopically analysed. Its diameter of 0.6 mm and its length of the free standing part of 10 mm are the typical dimensions of electrodes for high-intensity discharge lamps. This paper gives a physical interpretation of the axially symmetric arc spot by a simulation of its properties with a cathodic sheath model which takes into account a reduction in the work function above a critical temperature of the cathode surface by a thorium ion current. At first the optical observation and spectroscopic investigations are recapitulated. Then, an overview is given on the essential elements which are needed to simulate the cathodic arc attachment on a hot electrode. A simulation of a central cathode spot with these elements gives results which are far away from the experimental findings if a constant work function φ is used. Therefore, a temperature-dependent work function φ(T) is introduced. This φ(T) transitions from 4.55 to 3 eV above temperatures of the order of 3000 K. With this emitter spot model a constricted arc attachment is obtained by simulation in the centre of the flat end face of the cathode in accordance with experiment. For currents below i arc,max ≈ 15.5 A, two spot solutions with different cathode falls are found. They form a current-voltage-characteristic consisting of two branches which extend from a turning point at i arc,max to lower currents. For i arc > i arc,max , only a diffuse mode of cathodic arc attachment is obtained. It is shown by a comparison with measured data for i arc = 7.5, 10, 12.5 and 15 A that the solution with the lower cathode fall is observed experimentally.

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Section: Introductionmentioning

confidence: 73%

“…The discharge assumes the shape of a free burning arc within the vessel. An overview of the experimental setup is given in [3], figure 3, or in [4], figure 3.…”

Section: Experimental Investigations and Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Simulation of the hot core mode of arc attachment at a thoriated tungsten cathode by an emitter spot model

Bergner

Scharf

Kühn

et al. 2014

Plasma Sources Sci. Technol.

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“…A more accurate estimation is expected using this revised formula as any inaccuracy in the measurement of intensity at the edges of a plasma column propagates to the estimated central axis temperature in case of Abel inversion. It is noted that the edges of a plasma column are usually prone to non-LTE (Ref [13][14][15][16][17]. The limitation of the formula is that it gives only axial temperature and cannot determine radial profile.…”

Section: Methodsmentioning

confidence: 99%

Temperature Profile in YPO4 Laden Plasma Jet and Its Evolution with Arc Current and Powder Loading

et al. 2021

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YPO 4 is emerging as one of the fittest candidates for anti-corrosion thermal-barrier coatings suitable for aggressive environments at high temperature. The study presents an in situ investigation of the axial distribution of temperature in an YPO 4 laden plasma jet using a modified Boltzmann plot technique that does not require Abel inversion and suited for jets involving instabilities and thermal non-equilibrium. Investigated operating current range (528 to 730 A) and powder flow rates (5.37 to 13.62 g/min) are found to ensure effective development of YPO 4 coating. The nozzle exit temperature is found to vary from 11000 to 15000 K depending on arc current and powder loading. With no powder loading, the axial temperature distribution mostly follows a Gaussian-like profile at all set currents. With powder feeding, the profiles get transformed into nearly linear drop with local spiking of temperature at several axial locations. The tendency becomes more intense at higher arc current. Formation of shock trains in the jet with powder loading is suspected to be the underlying reason behind spatial spiking of temperature. Exhibited poor dependence of the nozzle exit temperature on powder loading at lower arc currents is found to get reversed at higher arc currents.

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“…In consequence, many kinds of ions are simultaneously generated, e.g., H, H + , H 2 + , H 3 + , ArH + , Ar + , Ar 2+ , Ar * [28,30,31] in argon-hydrogen plasma. The temperature of the excited electron is often in order of magnitude of 10 3 ~ 10 5 K [32][33].…”

Section: Plasma Jetmentioning

confidence: 99%

A Study of the Influence of the Surrounding Gas on the Plasma Jet and Coating Quality During Plasma Spraying

Liu

Ansar

Arnold

2017

Plasma Chem Plasma Process

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Coating quality is affected by arc and plume instabilities during plasma spraying. In closed chamber plasma spraying, gradual drift is one of the intermediate instabilities, which is mainly due to the electrode erosion. This work focuses on the source of the gradual drift of the plasma jet and the influence on coating quality. The ambient state inside the chamber was controlled by a ventilation system and a vacuum system. The variation in the plasma jet was observed by a particle flux image (PFI) device based on a CCD camera. The optical spectrum of the plasma plume was measured and analyzed through an optical spectrometer. The results indicated that the addition of hydrogen to plasma gas induced the change in the plasma jet length and width with changing rates depending on the chamber state and the ventilation power. With poor ventilation, the intensity of H α emission was found to become gradually stronger while H β and H γ were found to become weaker. On closing the chamber and remaining enough ventilation power, it was observed that the ambient gas slowly turned red. Simultaneously, the coating weight and thickness were slightly decreased meanwhile the porosity ratio was obviously increased. The red ambient gas has been proved to be able to acidify the city water with pH value decreased from 7 to 1~3. Without hydrogen, the plasma jet was found to be stable without reddening and variation, but the plasma enthalpy was unfortunately low.

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A spatially resolved relaxation method for pLTE plasma diagnostics in free-burning arcs

Cited by 18 publications

References 46 publications

Simulation of the hot core mode of arc attachment at a thoriated tungsten cathode by an emitter spot model

Simulation of the hot core mode of arc attachment at a thoriated tungsten cathode by an emitter spot model

Temperature Profile in YPO4 Laden Plasma Jet and Its Evolution with Arc Current and Powder Loading

A Study of the Influence of the Surrounding Gas on the Plasma Jet and Coating Quality During Plasma Spraying

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