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Seifter, Achim; Sachsenhofer, Franz; Pottlacher, Gernot

doi:10.1023/a:1019852506410

Cited by 21 publications

(16 citation statements)

References 7 publications

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“…Based on these Stokes parameters, the optical constants of an opaque sample at a given laser wavelength, perpendicular to the sample's surface, n and k, and further on, emissivity ε are calculated, resulting in the normal spectral emissivity at the used laser wavelength of 684.5 nm. Further details about the setup and the overall formalism are given in [7,8], normal spectral emissivity results for pure metals in [1,2,9], for the binary Fe-Ni system in [3], and first systematic investigations for high alloyed Ni-and Fe-based alloys are given in [4].…”

Section: Methodsmentioning

confidence: 99%

Normal Spectral Emissivity of Steel HS2-9-1-8 at 684.5 nm

et al. 2011

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Within this study, the normal spectral emissivity at melting and in the liquid state of the highly alloyed steel HS2-9-1-8 at 684.5 nm is presented. Measurements were performed with a division-of-amplitude photopolarimeter, as part of a fast ohmic pulse heating system reaching heating rates of about 10 8 K · s −1 . The determined data show an increasing emissivity throughout the liquid phase, with the value at liquidus T liquidus = 1687 K being ε = 0.371 and at the highest temperature T max = 2307 K of ε = 0.404. This trend was approximated by a linear least-squares fit yielding ε(T) = 0.282 + 52.88 × 10 −6 T. Although the ε-value at melting is similar to pure iron, the increase in ε with temperature is much higher for HS2-9-1-8 and should be taken into account whenever better accuracies are needed for optical temperature measurements.

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Section: Methodsmentioning

confidence: 99%

Normal Spectral Emissivity of Steel HS2-9-1-8 at 684.5 nm

et al. 2011

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“…3), then measuring the temperature at long wavelengths exclusively is not a remedy to this problem. It is known from the literature [12] that the normal spectral emissivity in most cases increases with temperature and hence the assumption of a constant emissivity in order to obtain Eq. (3) is not valid.…”

Section: Simple Model For Temperature Non-uniformitiesmentioning

confidence: 99%

About the Proper Wavelength for Pyrometry on Shock Physics Experiments

Seifter

Obst

2007

Int J Thermophys

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Usually one wants to measure the thermal radiance emitted by a hotsurface at a wavelength as short as possible, since the uncertainty in the true temperature due to unknown emissivity decreases with decreasing wavelength. Unfortunately the radiance also decreases with decreasing wavelength, and hence the signal-to-noise ratio becomes worse with shorter wavelengths. Depending on what temperature range is to be covered, a reasonable compromise can be found for most applications. When pyrometry is applied to shock physics experiments, there is an additional factor that has to be taken into consideration. Due to the nature of shock physics experiments, one has to deal with background light caused by flashes from air lighting up, highexplosive light, and muzzle flash from a powder gun, etc. In addition, even if the experiment is designed appropriately, there is often a temperature nonuniformity as well as thermal radiation from transparent anvils that are used to increase the interface pressure. In most cases, there is no engineering approach to minimize these temperature non-uniformities. The sensitivity to these non-uniformities increases with decreasing wavelength for the very same reason that the sensitivity to uncertainties in emissivity is increasing. This paper describes the above problems, deals with the problem of temperature non-uniformity in detail, and presents arguments why single-wavelength pyrometry in shock physics experiments can be very deceiving even in well designed experiments.

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“…At the end of melting our measured value is 0.847 µΩ·m, yielding an increase of ρ = 0.203 µΩ·m upon melting. For electrical resistivity that is compensated for thermal volume expansion (index VE), ρ VE, we used literature values for the thermal expansion of iridium from Wimber [17] and density data from Ishikawa et al [18] 6 . The increase in diameter, due to thermal expansion, results in a shift to higher resistivity values, as the actual cross section of the wire, which affects the measured electrical resistance of the samples, is increased.…”

Section: Resultsmentioning

confidence: 99%

“…We refrained from showing a graph of thermal diffusivity vs. temperature, as all relevant information about a can 6 Ishikawa et al published two different papers presenting density data for liquid iridium within a period of a couple of months [18,19] in which the values disagree considerably. Contacting the authors directly, they informed us that the values in Ref.…”

Section: Resultsmentioning

confidence: 99%

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Thermophysical Properties and Normal Spectral Emittance of Iridium up to 3500 K

Cagran

Pottlacher

2007

Int J Thermophys

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An ohmic pulse-heating experiment together with radiometry and µs-photopolarimetry is deployed at the Institute of Experimental Physics, Graz University of Technology, to obtain temperature-dependent thermophysical properties of conducting samples in the solid and molten states. This experimental setup has been used within the present work to gather data for solid and liquid iridium. Results for both thermophysical properties, as well as the normal spectral emittance obtained at a wavelength of 684.5 nm up to 3500 K are reported. The newly obtained values for iridium are presented in graphical and tabular form and compared to available literature data. The uncertainties for all reported properties are stated and it follows that, considering these expanded uncertainties, the recent data are in very good agreement with literature sources. Mutually motivated by these good results and by the scarce (if any) data available for the liquid state, the thermal conductivity and thermal diffusivity of liquid iridium are estimated by means of the WiedemannFranz law.

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Cited by 21 publications

References 7 publications

Normal Spectral Emissivity of Steel HS2-9-1-8 at 684.5 nm

Normal Spectral Emissivity of Steel HS2-9-1-8 at 684.5 nm

About the Proper Wavelength for Pyrometry on Shock Physics Experiments

Thermophysical Properties and Normal Spectral Emittance of Iridium up to 3500 K

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