Precision terahertz relative reflectometry using a blackbody source and heterodyne receiver

Woskov, P.; Cohn, D.R.; Han, S. C.; Gatesman, Andrew J.; Giles, Robert H.; Waldman, J.

doi:10.1063/1.1145153

Cited by 5 publications

(2 citation statements)

References 3 publications

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“…It would be much more desirable to use incoherent radiation to probe the magnitude of emissivity. It was shown that incoherent blackbody radiation could be used for precision terahertz reflectivity measurements of high temperature superconductors [4]. In the present work we show that the thermal emission from the viewed sample can be redirected back to the sample and used to probe its emissivity and consequently resolve the parameters of the thermal emission product εT.…”

Section: Introductionmentioning

confidence: 79%

Thermal return reflection method for resolving emissivity and temperature in radiometric measurements

Woskov

Sundaram

2002

Journal of Applied Physics

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A radiometric method for resolving the emissivity, ε, and temperature, T, in thermal emission measurements is presented. Thermal radiation from a viewed source is split by a beamsplitter between a radiometer and a mirror aligned to return a part of the thermal radiation back to the source. The ratio of the thermal signal with and without a return reflection provides a measurement of the emissivity without need of any other probing sources. The analytical expressions that establish this relationship are derived taking into account waveguide/optic losses and sources between the radiometer and viewed sample.The method is then applied to thermal measurements of several refractory materials at temperatures up to 1150 °C. A 137 GHz radiometer is used to measure the emissivity and temperature of an alumina brick, an Inconel 690 plate, and two grades of silicon carbide. Reasonable temperature agreement is achieved with an independent thermocouple measurement. However, when the emissivity approaches zero, as in the case of the Inconel plate, radiometric temperature determinations are inaccurate, though an emissivity near zero is correctly measured. This method is expected to be of considerable value to non-contact thermal analysis applications of materials.2

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Section: Introductionmentioning

confidence: 79%

Thermal return reflection method for resolving emissivity and temperature in radiometric measurements

Woskov

Sundaram

2002

Journal of Applied Physics

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“…Polarization sensitive measurements could unambiguously track anisotropic material characteristics. Past work has applied MMW techniques to nuclear waste glass melter measurements [10], water-ice freezing dynamics [11], and precision high-temperature superconductor resistivity measurements [12].…”

Section: Millimeter-wave Approachmentioning

confidence: 99%

Millimeter-Wave Thermal Analysis Development and Application to GEN IV Reactor Materials

Wosko¹,

Sundram²

2012

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New millimeter-wave thermal analysis instrumentation has been developed and studied for characterization of materials required for diverse fuel and structural needs in high temperature reactor environments such as the Next Generation Nuclear Plant (NGNP). A two-receiver 137 GHz system with orthogonal polarizations for anisotropic resolution of material properties has been implemented at MIT. The system was tested with graphite and silicon carbide specimens at temperatures up to 1300 ºC inside an electric furnace. The analytic and hardware basis for active millimeter-wave radiometry of reactor materials at high temperature has been established. Real-time, non contact measurement sensitivity to anisotropic surface emissivity and submillimeter surface displacement was demonstrated. The 137 GHz emissivity of reactor grade graphite (NBG17) from SGL Group was found to be low, ~ 5 %, in the 500-1200 °C range and increases by a factor of 2 to 4 with small linear grooves simulating fracturing. The low graphite emissivity would make millimeter-wave active radiometry a sensitive diagnostic of graphite changes due to environmentally induced stress fracturing, swelling, or corrosion. The silicon carbide tested from Ortek, Inc. was found to have a much higher emissivity at 137 GHz of ~90% Thin coatings of silicon carbide on reactor grade graphite supplied by SGL Group were found to be mostly transparent to millimeter-waves, increasing the 137 GHz emissivity of the coated reactor grade graphite to about ~14% at 1250 ºC.

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Convertible transmission-reflection time-domain terahertz spectrometer

Khazan¹,

Meissner²,

Wilke³

2001

Review of Scientific Instruments

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Precision terahertz relative reflectometry using a blackbody source and heterodyne receiver

Cited by 5 publications

References 3 publications

Thermal return reflection method for resolving emissivity and temperature in radiometric measurements

Thermal return reflection method for resolving emissivity and temperature in radiometric measurements

Millimeter-Wave Thermal Analysis Development and Application to GEN IV Reactor Materials

Convertible transmission-reflection time-domain terahertz spectrometer

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