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Radiometric Measurement of Thermodynamic Temperatures in the Temperature Range from 419 °C to 660 °C for an Improved Temperature Scale

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Radiometric Measurement of Thermodynamic Temperatures in the Temperature Range from 419 °C to 660 °C for an Improved Temperature Scale Radiometric Measurement of Thermodynamic Temperatures in the Temperature Range from 419 °C to 660 °C for an Improved Temperature Scale vorgelegt von M.Sc. Narudom Noulkhow aus Suratthani (Thailand) Der Fakultät II - Mathematik und Naturwissenschaften der Technischen Universität Berlin zur Erlangung des akademischen Grades Doktor der Ingenieurwissenschaften -Dr.-Ing.- genehmigte Dissertation Promotionsausschuss: Vorsitzender: Prof. Dr. U. Woggon Berichter/Gutachter: Prof. Dr. A. Hoffmann Berichter/Gutachter: Prof. Dr. C. Thomsen Tag der wissenschaftlichen Aussprache: 10. Dezember 2009 Berlin 2009 D 83 Abstract The International Temperature Scale of 1990 (ITS-90), as a practical temperature scale, is a very good approximation of the true thermodynamic temperature. It is based on the phase transition temperatures of its defining fixed-points and interpolating and extrapolating instruments for the temperature measurement between and above these fixed-points. However, at the time the ITS-90 was established, the freezing points of tin and zinc had been measured twice, in 1976 and in 1989 at the National Institute of Standard and Technology (NIST) with a gas thermometer, and at a reference temperature of 730 K these two measurements gave significantly different results of 30 mK. Since no primary thermometry other than gas thermometry was available at that time in this temperature range, the Consultative Committee for Thermometry (CCT) decided to use the average value between these two measurements for the reference temperature of the ITS-90 at 730 K with a standard uncertainty of 15 mK with respect to thermodynamic temperature. This uncertainty is passed on and increases for the thermodynamic temperature determination of fixed-points with higher temperatures by radiation thermometry. In order to prepare a new improved practical temperature scale anticipated for the year 2011, possible deviations of the ITS-90 from the thermodynamic temperature have to be investigated with an accurate primary thermometry method, independent from gas thermometry. This work contributes to solve the problem of the systematic deviation of 30 mK between the two gas thermometry measurements of the reference temperature at 730 K by applying absolute radiation thermometry as an independent primary thermometry method. To achieve this, two narrow-bandwidth filter radiometers based on InGaAs photodiodes working at 1300 nm and 1550 nm were realized and a double heat-pipe blackbody radiator was used as a high-accuracy source of thermal radiation in the temperature range from 692 K to 933 K. This temperature range covers the important zinc-fixed-point (692.677 K) and aluminum-fixed-point (933.473 K). The filter radiometers were calibrated in terms of their spectral irradiance responsivity traceable to the most accurate primary detector standard, a cryogenic electrical substitution radiometer. A newly developed tuneable laser- and monochromator based - cryogenic radiometer facility allowed to reduce the relative standard uncertainty of the near infrared spectral responsivity scale to 0.03%. For the determination of the deviation of the ITS-90 temperature from the thermodynamic temperature a standard uncertainty of about 30 mK at 692 K and 60 mK at 933 K was achieved. With these radiometric measurements the set of gas thermometry measurements by Edsinger and Schooley in 1989 clearly agrees, while the gas thermometry results by Guildner und Edsinger in 1979 disagree. i ii Zusammenfassung Die internationale Temperaturskala von 1990 (ITS-90) ist als praktische Temperatur- skala eine sehr gute Näherung der thermodynamischen Temperatur. Sie basiert auf den Phasenübergangstemperaturen definierender Fixpunkte und Messverfahren der Inter- und Extrapolation für die Temperaturmessung zwischen und oberhalb dieser Fixpunkte. Zu der Zeit als die ITS-90 erstellt wurde, wurde die Erstarrungstemperatur von Zinn und Zink zweimal (1976 und 1989) am National Institute of Technology (NIST) mit einem Gasthermometer gemessen. Zwischen diesen beiden Messungen bestand ein signifikanter Unterschied von 30 mK bei einem Referenzwert von 730 K. Da zum damaligen Zeitpunkt und in diesem Temperaturbereich keine andere, von der Gasthermometrie unabhängige, primärthermometrische Methode zur Verfügung stand, wurde vom Consultative Committee for Thermometry (CCT) für die ITS-90 als primärthermometrischer Referenzwert bei 730 K der Mittelwert der beiden Messungen, mit einer Unsicherheit bezüglich der thermodynamischen Temperatur von 15 mK festgelegt. Durch die quadratische Fehlerfortpflanzung wirkt sich die Unsicherheit des Referenzwertes bezüglich der thermodynamischen Temperatur im Hochtemperaturbereich besonders deutlich aus. Für eine neue, verbesserte praktische Temperaturskala, müssen mögliche Abweichungen der ITS-90 von der thermodynamischen Temperatur mit genauen primärthermometrischen Methoden untersucht werden, die von der Gasthermometrie unabhängig ist. Diese Arbeit trägt dazu bei, mit einer von der Gasthermometrie unabhängigen primärthermometrischen Methode, der spektralradiometrischen Messung thermodynamischer Temperaturen an einem Schwarzen Strahler, das Problem der systematischen Abweichung zwischen den beiden gasthermometrisch am NIST bestimmten Werten für die thermodynamische Temperatur des ITS-90- Referenzwertes zu lösen. Dazu wurden zwei schmalbandige Filterradiometer, die auf InGaAs Photodioden basieren mit den Schwerpunktwellenlängen 1300 nm und 1550 nm aufgebaut und ein Doppel-Wärmerohr-Hohlraumstrahler wurde als genaue Quelle von thermischer Strahlung im Temperatursbereich zwischen dem Zink- Fixpunkt (692.677 K) und dem Aluminium-Fixpunkt (933.473 K) eingesetzt. Die Filterradiometer wurden bezüglich ihrer der spektralen Bestrahlungsstärke- empfindlichkeit kalibriert, d.h. rückgeführt auf ein bei sehr tiefen Temperaturen betriebenes (∼5 K) elektrisches Substitutionsradiometer (Kryoradiometer) als Detektor-Primärnormal. An einem neuentwickelten Laser- und Monochromator gestützten Kryoradiometermessplatzes konnte die relative Standardunsicherheit der spektralen Empfindlichkeitskala im nahen Infrarot um den Faktor 6 auf 0.03% verringern werden. Bei der Bestimmung der Abweichung zwischen der ITS-90 Temperatur und der thermodynamischen Temperatur wurde eine Standard- unsicherheit von 30 mK bei 692 K und 60 mK bei 933 K erzielt. Das Ergebnis dieser Arbeit für die thermodynamische Temperatur des Referenzwertes stimmt mit dem von Edsinger und Schooley 1989 am NIST erzielten Resultat sehr gut überein. Das Ergebnis von Guildner und Edsinger 1976 am NIST hingegen weicht signifikant davon ab. iii iv Contents 1. Introduction 1 2. Theory and measurement concept 5 2.1 Thermodynamic temperature………………………………………..…..…………..5 2.2 Measurement of the thermodynamic temperature………………………………...9 2.3 The International Temperature Scale……..…………………………………........12 2.4 Radiation thermometry……………………………………………….……………..17 2.5 Requirements for the detectors……………..…………………………..…………25 3. Objective of this work 31 4. Measurement of the spectral responsivity in the NIR spectral range 33 4.1 Transfer detector………………………………………………………………….....33 4.2 Cryogenic radiometer………………………………………………………...……..34 4.3 Apparatus………………………………………………………………………….....36 4.4 High accuracy calibration of InGaAs transfer-detectors....................................41 4.5 Improvement of spectral responsivity calibration in the NIR spectral range….……………………………………………………………………………....45 4.6 Uncertainty of the spectral responsivity............................................................48 5. InGaAs filter radiometers 57 5.1 Design………………………………………………………………………...……....57 5.2 Calibration of the spectral irradiance responsivity.............................................62 5.3 Uncertainty of the filter radiometer calibration..................................................79 v 6. Thermodynamic temperature determination 85 6.1 Principle............................................................................................................85 6.2 The radiation source.........................................................................................87 6.3 Experimental setup...........................................................................................94 6.4 Radiometric measurement of thermodynamic temperature………...................98 6.5 Measurement of the ITS-90 temperature T90………………….…………….….104 6.6 The deviation of T90 from the thermodynamic temperature………..………….110 7. Summary 139 Bibliography 143 Acknowledgement 153 vi List of Abbreviations BIPM Bureau International des Poids et Mesures, International Bureau of Weights and Measures (the international body responsible for metrology) CCT Comité Consultatif de Thermometrie, Consultative Committee on Thermometry (a consultative committee of the BIPM) CGPM Conférence Générale des Poids et Mesures, General Conference on Weights and Measures (held every 4 years at BIPM by representatives of the governments of all member states) CODATA Committee on Data for Science and Technology CRI Cambridge Research and Instrumentation (New type of cryogenic radiometer applied in this work) CVGT Constant volume gas thermometer DCGT Dielectric-constant gas thermometer DVM Digital volt meter EPT-76 The 1976 Provisional 0.5 K to 30 K Temperature Scale ESR Electrical substitution radiometer FIR Far-infrared FP Fixed-point FR Filter radiometer FWHM Full width at half maximum He-Ne laser Helium-neon laser IPTS-48 The International Practical Temperature Scale of 1948 IPTS-68 The International Practical Temperature
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