Abstract: It is advantageous to operate the thermodynamic cycle of an aeroengine at as high a turbine entry temperature as practical for the current metallurgical limits of the turbine blades, in order to achieve peak cycle efficiency and thus lower specific fuel consumption. However, achieving the highest possible turbine entry temperature requires accurate knowledge of the turbine blade temperatures for control purposes to prolong component life, as frequent excursions beyond the design limits of the blades can severely reduce their service life. The optical pyrometry technique represents the best method for providing these crucial temperature data needed for blade condition based monitoring. However, this method of non-contact temperature measurement is subject to a number of errors inherent to the gas turbine operating environment. In this paper we present the general operating principles and an overview of the measurement errors associated with optical pyrometry, together with a discussion of the techniques to prevent, limit and compensate for such errors resulting from the turbine environment.

Abstract: Rapid thermal annealing (RTA) with a short dwell time at maximum temperature is used with ion implantation to form shallow junctions and polycrystalline-Si gate electrodes in complementary, metal-oxide semiconductor (CMOS) Si processing. Wafers are heated by electric lamps or steady heat sources with rapid wafer transfer. Advanced methods use "spike anneals," wherein high-temperature ramp rates are used for both heating and cooling while also minimizing the dwell time at peak temperature to nominally zero. The fast thermal cycles are required to reduce the undesirable effects of transient-enhanced diffusion (TED) and thermal deactivation of the dopants. Because junction profiles are sensitive to annealing temperature, the challenge in spike annealing is to maintain temperature uniformity across the wafer and repeatability from wafer to wafer. Multiple lamp systems use arrayed temperature sensors for individual control zones. Other methods rely on process chambers that are designed for uniform wafer heating. Generally, sophisticated techniques for accurate temperature measurement and control by emissivity-compensated infrared pyrometry are required because processed Si wafers exhibit appreciable variation in emissivity.

Abstract: Fast x-ray scattering measurements on molten alumina were performed on the H10 beam line at the DCI Synchrotron of LURE (Orsay, France). A high-temperature chamber with a levitation device was coupled with the four-circle goniometer of the beam line. A 100 W CO2 laser was used to melt the sample and the temperature was measured using an optical pyrometer operating at 0.85 μm. Usually, measurements of the total structure factor S(Q) on molten materials are performed using a fixed detector scanned over an angular range. In this work, in order to reduce the total scan duration, x-ray scattered intensities were measured with a 120° position sensitive detector (INEL CPS120). We performed several measurements with different acquisition times varying from 10 s to 5 min. In 5 min it was possible to obtain a good determination of S(Q) with a usable signal up to the Q range limit (13 A−1). The intensity was comparable with a 1 h measurement with a NaI (Tl) scintillator scanned over the 120° 2θ range. On reducing th...

Abstract: A method and apparatus for heating semiconductor wafers in thermal processing chambers. The apparatus includes a non-contact temperature measurement system that utilizes radiation sensing devices, such as pyrometers, to determine the temperature of the wafer during processing. The radiation sensing devices determine the temperature of the wafer by monitoring the amount of radiation being emitted by the wafer at a particular wavelength. In accordance with the present invention, a spectral filter is included in the apparatus for filtering light being emitted by lamps used to heat the wafer at the wavelength at which the radiation sensing devices operate. The spectral filter includes a light absorbing agent such as a rare earth element, an oxide of a rare earth element, a light absorbing dye, a metal, or a semiconductor material.

Abstract: The structure and material properties of spray formed products depend directly on the thermal state of particles before they impact the substrate or on the already deposited layer Monitoring particle temperature, velocity and size can thus provide a unique tool for optimizing the material properties as well as controlling spraying conditions during deposition In this paper, an optical sensing device based on the principle of high-speed pyrometry, developed for on-line monitoring of particle temperature, velocity and diameter of in-flight particles during thermal spraying conditions (eg plasma guns), is for the first time applied and examined in the spray forming process Thermal radiation emitted by the particles is collected by a sensing head attached to the spray cone and transmitted through optical fibers to a detection cabinet located away from the dusty environment Tests were carried out with different materials, spray pressures and measurement positions to exhibit the efficiency of the measurement system in the spray forming process

Abstract: Temperature is a basic parameter in physics, but in the case of shock-compressed metals its measurement remains difficult and controversial Improvements in accuracy of a high-speed optical pyrometer enabled us to study interesting features of bismuth: temperatures of shock-loaded samples measured through a lithium-fluoride anvil and (indirectly) part of the fusion curve An improved method of analyzing optical pyrometry data is also discussed

Abstract: The families of titanium aluminide intermetallic alloys have attractive high temperature mechanical properties which make them potential candidate materials for a wide range of applications, particularly in the aeronautic and automobile sectors. The development of appropriate manufacturing techniques is an essential stage in the engineering exploitation of these materials, e.g., Induction Skull Melting is one of the techniques which needs to be optimised for the casting of titanium aluminides. Research is underway to develop a computer model of this process but data are required for the key thermophysical properties. Pulse-heating techniques have been used to measure properties for the Ti–44Al–8Nb–1B system. Rectangular samples have been prepared and are resistively heated as part of a fast capacitor discharge circuit. Time-resolved measurements with sub-μs resolution of currents through the specimen were made with a Pearson probe current monitor using the induction principle. Voltages across the specimen were determined with knife-edge contacts and voltage dividers, and radiance temperatures of the sample were measured with a pyrometer. These measurements allow the calculation of specific heat and dependencies between enthalpy, electrical resistivity and temperature of the alloy up into the liquid phase. Data for thermal diffusivity have been obtained by using the Wiedeman–Franz relation. The results are compared with those obtained using DSC and the four-probe method to measure the temperature dependence of the resistivity.

Abstract: Advances in digital imaging technology have enabled the development of sensors that can measure the temperature and velocity of individual thermal spray particles over a large volume of the spray plume simultaneously using imaging pyrometry (IP) and particle streak velocimetry (PSV). This paper describes calibration, uncertainty analysis, and particle measurements with a commercial IP-PSV particle sensor designed for measuring particles in an air plasma spray (APS) process. Yttria-stabilized zirconia (YSZ) and molybdenum powders were sprayed in the experiments. An energy balance model of the spray torch was used to manipulate the average particle velocity and temperature in desired ways to test the response of the sensor to changes in the spray characteristics. Time-resolved particle data were obtained by averaging particle streaks in each successive image acquired by the sensor. Frame average particle velocity and temperature were found to fluctuate by 10% during 6 s acquisition periods. These fluctuations, caused by some combination of arc instability, turbulence, and unsteady powder feeding, contribute substantially to the overall particle variability in the spray plume.

Abstract: The microsecond pulse heating system has been used for more than 15 years to investigate thermophysical properties of solid and liquid metals and alloys. The only way to measure temperature in the time and temperature range of these experiments (duration of a few tens of microseconds, temperatures up to 7000 K) is optical pyrometry. The radiance temperature can be measured very accurately. However, to obtain true temperature from radiance temperature the normal spectral emissivity at the wavelength of interest of the material under investigation has to be known. Because normal spectral emissivity measurements on pulse heated liquid metals were not possible in the past, an assumption about the behavior of the emissivity in the liquid phase had to be made, which increased the uncertainty of the temperature determination. To overcome this limitation in temperature measurement, a microsecond division of amplitude polarimeter (µ-DOAP) was added to the pulse heating system. The normal spectral emissivity at 684.5 nm is derived from the measured change in the state of polarization of laser light that is reflected off the sample surface. The working principle of this polarimeter system is presented, and experimental results of the normal spectral emissivity at 684.5 nm as a function of radiance temperature at 650 nm are discussed.

Abstract: An accurate method for melting-point measurement of refractory nuclear ceramics was developed, based on laser-pulse heating and thermal arrest detection. The temperature measurement is performed by a combined use of a brightness pyrometer and a high-speed spectrometer working in the range of 500 to 900 nm. This method provides both the true temperature and the spectral emissivity function of the examined materials. Pure sintered MgO and a Mg:Am mixed oxide were first measured. The resulting melting point of the former (2350±20 K) is significantly higher than that commonly recommended and decreases with the addition of americium. Furthermore, UO2 irradiated to 37,000 MWd/t and submitted to a reactor loss-of-coolant test was investigated: the melting point decreases from 3120 K, in the as-fabricated state, to 2950 K. Both fresh Zr:U mixed oxides and “corium” lava from a reactor meltdown experiment were also investigated.

Abstract: The object of the invention is to measure temperature using pyrometers, in a simple and economic way, enabling precise temperature measurement, even for low temperatures. The invention presents a device and method for thermally treating substrates, wherein the substrate is exposed to at least a first and at least a second radiation; the predetermined wavelengths of the first radiation are absorbed between the first radiation source and the substrate; a radiation from the substrate is measured in the predetermined wavelength using a radiation detector arranged on the same side as a second radiation source; the second radiation from the second radiation source is modulated and determined.

Abstract: Oxidation of turbine buckets may cause unexpected and expensive turbine failures Turbine bucket oxidation condition may be estimated to predict remaining useful bucket life during operation of a turbine by processing time-varying temperature distributions measured with a pyrometer of at least one rotating turbine bucket

Abstract: Ignition and combustion of pyrotechnic mixtures in a closed volume were carried out by squib type devices. Measurements and numerical simulations in a previous study showed that the phenomenon is very fast with durations of about 200 μs. The objective of this work is to present temperature measurements obtained by means of a two-color pyrometer. A specific pyrometric device was built to carry out these measurements, analyzing the radiation emitted by the pyrotechnic flame. It was concluded that the phenomenon is primarily controlled by the emission of particles. The radiation peculiar to the gases, inside the flame, is negligible. From these assumptions, a method can be established enabling to process the voltage signals from the pyrometer. The measuring apparatus was validated for very short response times in the order of μs. The temperature measured this way seems to reach a constant level for the first 50 μs of combustion. The luminance signals then continue to increase and a decrease in the temperature which reaches approx. 3000 K is observed.

Abstract: A high‐speed, four‐wavelength pyrometer has been developed for dynamic temperature measurements on samples that are heated by shock compression. The pyrometer uses a pair of off‐axis parabolic mirrors to collect radiance emitted from a target of 1 mm in diameter. A single optical fiber delivers the collected radiant flux to the detector housing. Three dichroic beam splitters are used to spectrally split the light into four beams that are then focused onto an equal number of LN2‐cooled InSb photodetectors. Broad bandwidth interference filters that are nominally centered at 1.8, 2.4, 3.4, and 5.0 μm define the wavelength ranges of the four channels. The blackbody‐temperature threshold of the pyrometer is at about 400 K. The signals are recorded at intervals as short as 20 ns using a four‐channel digital oscilloscope. Procedures for calibration and temperature measurements are described.

Abstract: A long-wavelength pyrometer is developed for the measurement of surface temperatures on materials that are semitransparent at lower wavelengths, and specific application is made to a dense zirconia ceramic (Mg-PSZ) undergoing laser-assisted machining (LAM). The pyrometer operates in a waveband between 11 and 14μm, and a detailed description of measurement uncertainties is provided. The largest uncertainties relate to knowledge of the surface emissivity and the large temperature gradients generated by the LAM process. Repeatability of the measurements is demonstrated, and a parametric study of three LAM parameters reveals expected trends, with good agreement between the measurements and predictions based on a model of the LAM process.© 2002 ASME

Abstract: A millisecond pulse-heating apparatus is presently under development at the Harbin Institute of Technology (HIT). The design is based on systems previously developed both at NIST (U.S.A.) [1, 2] and IMGC (Italy) [3] for the measurement of several thermophysical properties with millisecond time resolution. The apparatus uses rapid resistive self-heating of a strip-shaped specimen from room temperature to a pre-chosen maximum temperature. Power is furnished by a subsecond-duration electrical current pulse through the specimen. Simultaneous measurements are carried out for several quantities. The maximum current is up to 2000 A. Experiments are performed on strip-shaped specimens with the following typical dimensions: 80 mm in length, 10 mm in width, and 1 mm in thickness. The specimen is contained in a large vacuum chamber (bigger than 300 mm in both diameter and height) whose inner wall is coated with a nonreflecting paint. A special designed high-speed pyrometer will be used to measure the temperature of the specimen through one of two quartz windows of the chamber. The heat capacity, the electrical resistivity, the total hemispherical emissivity, and normal spectral emissivity of the specimen are measured by using this apparatus for various materials.

Abstract: Laser surface hardening is a process in which a shaped laser beam is scanned across the surface of a hardened component. The beam heats the surface rapidly to the austenite phase, while the rest of the component remains close to room temperature. The heat conducts to the surrounding material and the surface cools down very quickly forming a martensitic layer to the surface.Defining and controlling the absorption of the beam is important since all of the heating energy is brought to the material through absorption. Even small variations in the absorption change the laser power needed by hundreds of watts.In this study the absorption has been measured by a liquid calorimeter and the surface temperature has been measured with a dual wavelength pyrometer. The processing parameters used were the intensity of the beam, the interaction time and the angle between the beam and the surface. Surface temperatures during hardening varied from the Ac1 temperature to the melting point. Tests were done with a 3kW diode laser with a 10x5 mm hardening optic.Laser surface hardening is a process in which a shaped laser beam is scanned across the surface of a hardened component. The beam heats the surface rapidly to the austenite phase, while the rest of the component remains close to room temperature. The heat conducts to the surrounding material and the surface cools down very quickly forming a martensitic layer to the surface.Defining and controlling the absorption of the beam is important since all of the heating energy is brought to the material through absorption. Even small variations in the absorption change the laser power needed by hundreds of watts.In this study the absorption has been measured by a liquid calorimeter and the surface temperature has been measured with a dual wavelength pyrometer. The processing parameters used were the intensity of the beam, the interaction time and the angle between the beam and the surface. Surface temperatures during hardening varied from the Ac1 temperature to the melting point. Tests were done with a 3kW diode l...

Abstract: Shock compression and the following expansion into helium were used to generate the boiling of porous nickel. The brightness temperature and velocity of expansion were measured by a fast multichannel optical pyrometer. Gas dynamic peculiarities of expansion in the final pressure range below 0.4 GPa were studied. It has been proved that a shock rarefaction wave is formed under expansion when final states of the sample are inside the two-phase region. The fast heating of tungsten by multiple shocked helium in the process of acceleration of tungsten foil at dynamically formed isobaric conditions is proposed as a new way for generating near-critical-point states of liquid - vapour phase transition. Additionally, an estimation of the critical point data of tungsten is made.

Abstract: A transient interferometric technique to measure the thermal expansion of pure metals and alloys during rapid heating is presented. The metallic specimen is resistively heated from room temperature to a high temperature close to melting within approximately 500 ms by the passage of a high electrical current pulse. The temperature of the specimen is measured and time resolved by a fast pyrometer; the thermal expansion is obtained by a high-speed laser-interferometer. The device used is a modified polarized-beam Michelson-type interferometer with a phase-quadrature detector that distinguishes between expansion and contraction. Details of its principle, the construction, adjustment, and operation are described. In addition, thermal expansion measurements performed on molybdenum and tungsten standard reference materials (SRMs) are presented and compared with results obtained by other researchers.