Development of metal carbon high-temperature fixed-point blackbodies for precision photometry and radiometry

Abstract

High-temperature fixed-point blackbodies based on Re-C and TiC-C metal-carbon eutectic alloys are being investigated for use as radiance and irradiance sources for precise measurements in radiometry, photometry and radiation thermometry above the conventionally assigned values of temperatures on the ITS-90 scale. Graphite crucibles having inner diameters varying between 4 mm and 10 mm were used to prepare the metal-carbon and metal carbide-carbon eutectics; the cells were designed and manufactured at VNIIOFI, Russia using high-purity materials.The melting and solidification temperatures of the cells were measured. Their reproducibility was investigated. The radiance reproducibility of the Re-C and TiC-C fixed points was found to be from 0.01% to 0.03% at 650 nm wavelength depending on the cell. Preliminary investigations of ZrC-C fixed-point reproducibility have been carried out. The radiance of all measured cells agreed at the solidification point within 0.02%.

Blackbody Sources for the Range 100 K to 3500 K for Precision Measurements in Radiometry and Radiation Thermometry

“…3 presents a schematic section of the pyrolitic graphite cavity radiator with fixed-point cells installed. Measurements of Re-C, TiC-C and ZrC-C cells carried out at VNIIOFI [6] and also the results of bilateral intercomparisons with NPL demonstrated the reproducibility of spectral radiance at 650 nm at the 0.01 to 0.03 % level. The future applications of M-C / MC-C fixed-point blackbody cells are based on the possibility of binding the absolute spectral characteristics of sources, which are measured in different laboratories, to fixed-point blackbodies with an excellent reproducibility level exceeding 0.01%.…”

“…Since 2000 in VNIIOFI investigations have been carried out of fixed points based on M-C and MC-C eutectic alloys having phase-transition temperatures exceeding those of the conventional fixed points of the ITS-90 [6]. The crucibles containing Re-C (melting, 2748.5 K), Ir-C (2560.5 K) and TiC-C (melting, 3033.8 K), ZrC-C (melting, 3154.2 K) eutectic compositions were clutched between the pyrographite rings of radiators of BB3200pg/BB3500 used as a furnace.…”

Metrological support for climatic time series of satellite radiometric data

“…Thus, the experiments conducted at VNIIOFI with high-temperature alloys Re-C (T pt = 2748 K) and TiC-C (T pt = 3034 K) at the request of the National Metrology Institute of Japan 1 [16,17] showed the repeatability of SR measurements within 0.01% to 0.03% [18]. These results were later confirmed at VNIIOFI, the German Physicalisch-Technische Bundesanstalt, and at the National Physical Laboratory in Great Britain [19][20][21].…”

Investigation of Furnace Uniformity and its Effect on High-Temperature Fixed-Point Performance

“…The quality of a furnace, especially its temperature uniformity, is very critical for the reproducibility and plateau quality of the fixed points [3,4]. Three types of furnaces are conventionally used for the highest temperature M(C)-C fixed points: Thermogage, Nagano, and the VNIIOFI-made BB3200pg/BB3500 [5]. The last one was originally designed as a variable-temperature blackbody for spectral irradiance and later adapted as a furnace for HTFPs.…”