Measuring the temperature of microparticles in plasmas

Maurer, H. R.; Basner, R.; Kersten, Holger

doi:10.1063/1.2987688

Cited by 27 publications

(26 citation statements)

References 12 publications

(16 reference statements)

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“…But particularly in the experiments measuring grain charges the diagnostics of the hosting plasma is usually missing. In addition, although it is possible to measure the temperature of the grain [72], grain temperature and charge have not yet been measured simultaneously. For the microscopic modeling of surface charges it is however important to know at least these two quantities.…”

Section: Critiquementioning

confidence: 99%

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Physisorption kinetics of electrons at plasma boundaries

2009

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Abstract. Plasma-boundaries floating in an ionized gas are usually negatively charged. They accumulate electrons more efficiently than ions leading to the formation of a quasi-stationary electron film at the boundaries. We propose to interpret the build-up of surface charges at inert plasma boundaries, where other surface modifications, for instance, implantation of particles and reconstruction or destruction of the surface due to impact of high energy particles can be neglected, as a physisorption process in front of the wall. The electron sticking coefficient se and the electron desorption time τe, which play an important role in determining the quasi-stationary surface charge, and about which little is empirically and theoretically known, can then be calculated from microscopic models for the electron-wall interaction. Irrespective of the sophistication of the models, the static part of the electron-wall interaction determines the binding energy of the electron, whereas inelastic processes at the wall determine se and τe. As an illustration, we calculate se and τe for a metal, using the simplest model in which the static part of the electron-metal interaction is approximated by the classical image potential. Assuming electrons from the plasma to loose (gain) energy at the surface by creating (annihilating) electron-hole pairs in the metal, which is treated as a jellium half-space with an infinitely high workfunction, we obtain se ≈ 10 −4 and τe ≈ 10 −2 s. The product seτe ≈ 10 −6 s has the order of magnitude expected from our earlier results for the charge of dust particles in a plasma but individually se is unexpectedly small and τe is somewhat large. The former is a consequence of the small matrix elements occurring in the simple model while the latter is due to the large binding energy of the electron. More sophisticated theoretical investigations, but also experimental support, are clearly needed because if se is indeed as small as our exploratory calculation suggests, it would have severe consequences for the understanding of the formation of surface charges at plasma boundaries. To identify what we believe are key issues of the electronic microphysics at inert plasma boundaries and to inspire other groups to join us on our journey is the purpose of this colloquial presentation.PACS. 52.27.Lw Dusty or complex plasmas -52.40.Hf Plasma-material interaction, boundary layer effects -68.43.-h Chemi-/Physisorption: adsorbates on surfaces -73.20.-r Electron states at surfaces and interfaces

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Section: Critiquementioning

confidence: 99%

“…The particle temperature has to be of course within physically meaningful bonds. Recently, the particle temperature (but unfortunately not the particle charge) has been measured [72]. There is thus some hope that in the near future Z p and T s will be simultaneously measured.…”

mentioning

confidence: 99%

Physisorption kinetics of electrons at plasma boundaries

2009

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“…Oliver and Enikov measured the incandescent radiation from particles in a plasma jet, which of course is only possible at rather high particle temperatures above 1000 K [46]. A rather novel method for the measurement of particle temperatures utilizes temperature-sensitive spectral features of phosphor grains, which are excited by means of an external illumination source [33,44].…”

Section: Particles In a Plasma Environment And The Measurement Of Thementioning

confidence: 99%

“…For a quantitative description of particle heating in plasma environment the energy fluxes have to be measured either by calorimetric probes [2,48] or by suitable microparticle probes [44]. Based on probe theory for such test particles, a calorimetric balance model can be established where the particle temperature occurs as an observable.…”

Section: Particles In a Plasma Environment And The Measurement Of Thementioning

confidence: 99%

“…Several studies addressed the grain temperature, both theoretically [39][40][41][42] and experimentally [33,34,[43][44][45][46][47]. For example, Daugherty and Graves measured the temperature-dependent decay time of the fluorescence of manganese activated magnesium fluorogermanate particles in a pulsed argon discharge during the plasma-off phase [43].…”

Section: Particles In a Plasma Environment And The Measurement Of Thementioning

confidence: 99%

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On the heating of nano- and microparticles in process plasmas

Maurer¹,

Kersten²

2011

J. Phys. D: Appl. Phys.

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Determination and understanding of energy fluxes to nano-or microparticles, which are confined in process plasmas, is highly desirable because the energy balance results in an equilibrium particle temperature which may even initiate the crystallization of nanoparticles. A simple balance model has been used to estimate the energy fluxes between plasma and immersed particles on the basis of measured plasma parameters. Addition of molecular hydrogen to the argon plasma results in additional heating of the particles due to molecule recombination. The measured particle temperature is discussed with respect to appearing plasma-particle interactions which contribute to the particle's energy balance.

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Towards a Microscopic Theory of Particle Charging

Bronold¹,

Fehske

Kersten

et al. 2009

Contrib. Plasma Phys.

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We recently questioned the treatment of a dust particle as a perfect absorber for electrons and ions and proposed a surface model for the charge of a dust particle in a quiescent plasma which combines the microscopic physics at the grain boundary (sticking into and desorption from external surface states) with the macrophysics of the discharge (plasma collection fluxes). Within this model the charge and partial screening of the particle can be calculated without relying on the condition that the total electron collection flux balances on the grain surface the total ion collection flux. Grain charges obtained from our approach compared favorably with experimental data. The purpose of this paper is to describe our model in more detail, in particular, the hypotheses on which it is built, contrast it with the standard charging models based on flux balancing on the grain surface, and to analyze additional experimental data.

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Measuring the temperature of microparticles in plasmas

Cited by 27 publications

References 12 publications

Physisorption kinetics of electrons at plasma boundaries

Physisorption kinetics of electrons at plasma boundaries

On the heating of nano- and microparticles in process plasmas

Towards a Microscopic Theory of Particle Charging

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