Boris Khlevnoy

Application of metal (carbide)–carbon eutectic fixed points in radiometry

Metal (carbide)–carbon eutectic fixed points when applied to radiometry should operate at a temperature preferably exceeding 3000 K, have a large aperture, be robust and have long plateau duration. The large-tube-diameter BB3500YY furnace, recently introduced at the National Metrology Institute of Japan (NMIJ), has been tuned for such fixed-point realization. A novel cell structure with an internal insulation of highly purified carbon-composite sheet material was designed and tested. This resulted in improved robustness, immunity to furnace temperature nonuniformity and extended plateau duration. The design was applied to a hyper-eutectic porous ingot cell, and a reproducible plateau was observed. Preliminary results for a large aperture cell with an aperture diameter of 8 mm are also reported.

Investigation of high-temperature black body BB3200

During an international comparison of radiation temperature measurements performed at the AllRussian Institute for Optophysical Measurements (VNIIOFI), Moscow, in June 1997 by participants from the VNIIOFI, the National Physical Laboratory (NPL), Teddington, and the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, detailed measurements of the characteristics of two different types of high-temperature black-body source took place. Both of the black bodies consisted of a pyrolytic-graphite cavity and differed only in the design of the electrodes, which were either axial or coaxial. All investigations were carried out covering a temperature range from 1380 K to 3100 K. The electrical characteristics of the black bodies were investigated at all temperature points; and measurements of the temperature drift were performed to determine the stability of the systems in constant-current mode and in optical-feedback control mode. The uniformity of the black-body radiation field was measured in the radiance mode by using narrowband, interference-filter-based radiometers with imaging optics from the NPL and in the irradiance mode by using broadband-filter detectors from the PTB to scan the irradiated area. The results confirm the suitability of the BB3200 for both radiance and irradiance measurements at national metrological institutes.

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

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%.

Melting points of gallium and of binary eutectics with gallium realized in small cells

Melting/freezing curves are studied for the single-component Ga and bimetallic eutectic alloys Ga–In, Ga–Sn, Ga–Zn and Ga–Al in small-size cells. These phase-transition studies were conducted at VNIIOFI and SDL in order to design small-size fixed-point devices for metrological monitoring of temperature sensors on autonomous platforms. Our prime objective is to develop technology to improve the long-term performance of in-flight blackbody calibration sources of space-borne radiometers. The repeatability of the melting temperature of Ga and the eutectic melting temperatures of Ga–In, Ga–Sn and Ga–Zn fixed points were studied. Our results show that small cells containing Ga and some Ga-based eutectic alloys can be used as melting fixed-point standards.

Final report on the CCPR-S2 supplementary comparison of area measurements of apertures for radiometry

The accuracy of aperture area measurements is vital to many radiometric and photometric measurements. The Consultative Committee on Photometry and Radiometry (CCPR) undertook an international comparison of the methods by which member laboratories measure the areas of apertures used for radiometry. Nine laboratories measured eight different apertures varying in diameter size, fabrication method, material and edge type. This paper includes a description of the apertures used for the comparison, the results of the comparison categorized by artifact and by laboratory, and a brief discussion of the method used by each laboratory along with its uncertainty budget. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Intercomparison of radiation temperature measurements over the temperature range from 1600?K to 3300?K

An intercomparison of radiation temperature measurements was performed at VNIIOFI during October 2000 using a pyrolytic graphite blackbody operating over the temperature range from 1600?K to 3300?K. A pyrometer and two photometers from VNIIOFI, a pyrometer and four broadband glass filter detectors from PTB, and two narrow-band interference filter based radiometers and a broadband glass filter radiometer from NPL were used to perform the temperature measurements in either radiance or irradiance mode. Across almost the entire temperature range the VNIIOFI, NPL and PTB instruments showed results within the combined standard measurement uncertainties.

Development and investigation of WC–C fixed-point cells

Three cells of the WC?C peritectic fixed point with a temperature of about 3021?K were built and investigated. Two different sources of tungsten with nominal purities of 5N and 3N were used, and two different filling techniques were applied. There was no difference in plateau shapes between the cells. The 3N purity cell showed a small difference (0.22?K) in the melting temperature from the 5N cell, which indicates significant purification of initially contaminated tungsten. The typical melting range and repeatability of the observed peritectic melting plateaux were 100?mK and 15?mK, respectively. The melting point was stable and reproducible within 25?mK per two weeks. T90 temperature of the WC?C melting point was found to be (2747.6 ? 1.1)??C (k = 2). The observed freezing plateaux were flat and repeatable within 50?mK and 15?mK, respectively. The WC1?x?WC eutectic transition showed a melting temperature about 29?K lower than the peritectic one with a repeatability of about 0.2?K. The problem of deep supercooling is discussed and a method for its solution is shown and tested.

Performance limitations of carbon-cavity blackbodies due to absorption bands at the highest temperatures

It has been demonstrated that under specific conditions absorption bands in the spectrum of graphite high-temperature cavity radiators can be observed. These irregularities affect the Planckian spectra that are expected for a blackbody. Several investigations were made to investigate and to avoid these absorptions. It was shown that absorptions could be totally avoided at temperatures below 3100 K and, for some absorptions bands, even at higher temperatures. However, at temperatures above 3100 K, especially in the visible spectral range, absorption bands occur that unfortunately cannot be avoided. The absorptions have been identified to originate from molecular carbon that is increasingly subliming at the highest temperatures. These absorptions presently limit the use of graphite-based high-temperature radiators as ideal Planckian radiators.

International comparison of radiation-temperature measurements with filtered detectors over the temperature range 1380 K to 3100 K

A series of black-body radiation-temperature measurements has been made over the temperature range 1380 K to 3100 K using two different designs of pyrolytic-graphite black bodies with calculated emissivities of 0.999. All measurements were performed at the All-Russian Research Institute for Optophysical Measurements (VNIIOFI) during June 1997. A filter photometer from the VNIIOFI, broadband glass-filter detectors from the Physikalisch-Technische Bundesanstalt (PTB) and narrowband interference-filter-based radiometers from the National Physical Laboratory (NPL) were used to perform the temperature measurements in either radiance or irradiance mode using both black bodies. Across the entire temperature range, the NPL and PTB instruments showed consistent results with both black bodies and differing geometrical arrangements. Results from the VNIIOFI photometer were also broadly consistent for a wide temperature range.

The Global Earth Observation System of Systems (GEOSS) and metrological support for measuring radiometric properties of objects of observations

The international Global Earth Observation System of Systems is at its initial stage. We present some general information about the program and formulate the task of ensuring the uniformity of radiometric measurements to be conducted by all the participating national systems. Methods of solving the task are suggested on the basis of the wide application of standard sources that use phase transition of eutectic alloys and pure metals as well as with the help of improved ground calibration facilities.