Independent Temperature Measurements Research Articles

Simultaneous independent measurement of strain and temperature based on long-period fiber gratings inscribed in holey fibers depending on air-hole size

We propose and experimentally demonstrate a simple and flexible scheme for the simultaneous measurement of strain and temperature using long-period fiber gratings (LPFGs) based on versatile holey fibers (HFs) with different air-hole sizes. The strongly resonant LPFGs (as much as approximately 24 dB) can be successfully achieved. The LPFGs inscribed in the HFs have similar temperature sensitivities regardless of air-hole size because of the same material composition. The strain sensitivities of the LPFGs, however, are different, since holey fibers have different cross-sectional areas depending on the air-hole size. The strain sensitivities of the HF-based LPFGs are enhanced by a factor larger than 2 as the air-hole size increases.

Dual Bragg grating sensor for concurrent torsion and temperature measurement

The paper discusses a dual fibre Bragg grating sensor for the independent measurement of temperature and torsion in a rotating shaft. It shows theoretically that torsion affects the differential wavelength of the gratings in the proposed configuration, whereas temperature changes only the common-mode wavelength, allowing measurement of both torsion and temperature. For the particular system investigated experimentally, the differential wavelength change due to torque was 19.4 pm (N m)−1, and the corresponding temperature sensitivity was −0.36 pm °C−1. In contrast to these values, the temperature sensitivity of the common-mode wavelength change was 25.3 pm °C−1, and its torque cross-sensitivity was −0.19 pm (N m)−1.

Estimating turbulent dissipation rates from acoustic backscatter

Recent work has suggested the possibility of using high-frequency (10 kHz to 1 MHz) acoustics to remotely sense turbulent microstructure in the ocean. Once developed, this technique will provide a powerful tool for examining the spatial and temporal distributions of ocean mixing in a way not possible using traditional microstructure methods. In this paper turbulent dissipation rates are estimated through an inversion of 307 kHz acoustic scattering data collected in the lee of a sill in Knight Inlet, British Columbia. These data have been shown previously to be strongly correlated with temperature and shear microstructure measurements. Here we show that inversion methods can be used to get turbulent dissipation rates from acoustic backscatter, provided that independent measurements of temperature and salinity stratification are available. The temperature–salinity characteristics of the environment, however, can place limitations on the inversion technique. The strong negative salinity gradient in Knight Inlet decreases the slope of the functional relationship between dissipation rate and scattering cross-section for high dissipation rates and increases the uncertainty of the inversion. This limitation on the inversion technique is not an issue throughout most of the world's oceans (where d T / d S > 0 ) and, in places where it could be a problem, the limitation can be overcome by using multi-frequency techniques.

Simultaneous independent temperature and strain measurement using one fiber Bragg grating based on the etching technique

AbstractA new method for the simultaneous and independent measurement of temperature and strain that employs only one FBG based upon the etching technique is demonstrated both theoretically and experimentally. The sensor using this scheme has a small sensor probe, and offers combined characteristics of compactness, effective cost, and easy fabrication. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 478–481, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20507

Estimating internal wave statistics from underwater acoustic transmission scintillation measurements on the New Jersey shelf with a 3-D stochastic model

The acoustic intensity expected after transmission through random inhomogeneities in an ocean waveguide is analytically expressed in terms of modal dispersion, attenuation, and energy redistribution in a 3-D multiple forward scattering formulation [Ratilal and Makris, J. Acoust. Soc. Am. 114, 2428 (2003)]. This approach is used to model forward scattering through a random internal wavefield. Scattering from the density and compressibility inhomogeneities caused by the internal waves is approximated with the Rayleigh–Born series. The model is used to estimate the rms internal-wave height from low-to-mid-frequency underwater acoustic transmission scintillations measured during the Main Acoustic Clutter experiment of 2003 in the New Jersey Strataform area. Estimated internal wave height standard deviations matched those obtained from independent temperature and CTD measurements and suggest that the internal wave field was not temporally stationary.

A model-based noninvasive temperature estimation technique for monitoring HIFU therapy using backscattered ultrasound

A new noninvasive temperature estimation technique using the bioheat transfer equation (BHTE) to constrain inversion of ultrasonic travel time data has been developed for HIFU therapy monitoring. Initial estimates for BHTE parameters and ultrasonic travel time temperature dependence δτ(T) are noninvasively obtained in situ using ultrasound backscatter signals acquired during two probe heating exposures performed prior to therapy: one to obtain medium thermal parameters, the other to estimate the magnitude of the local HIFU heat source. These estimates are used in BHTE simulations and compared to local travel time changes measured periodically during therapy using a medical ultrasound imager. Quantitative 2-D temperature maps are obtained by constrained data fitting. Preliminary results obtained from in vitro experiments in tissue mimicking phantoms will be presented. Temperature maps are computed throughout therapy delivery and posttreatment cooling periods, and validated against independent temperature measurements obtained using thermocouples placed close to but not at the HIFU focus. This model-based technique permits temperature estimation throughout the entire therapeutic range and is completely noninvasive, and is thus a departure from previously reported techniques. This ultrasound-based approach could serve as an alternative to MRI-based temperature estimation methods in a clinical setting.

Temporal Homogenization of Monthly Radiosonde Temperature Data. Part II: Trends, Sensitivities, and MSU Comparison

Trends in radiosonde-based temperatures and lower-tropospheric lapse rates are presented for the time periods 1959‐97 and 1979‐97, including their vertical, horizontal, and seasonal variations. A novel aspect is that estimates are made globally of the effects of artificial (instrumental or procedural) changes on the derived trends using data homogenization procedures introduced in a companion paper (Part I). Credibility of the data homogenization scheme is established by comparison with independent satellite temperature measurements derived from the microwave sounding unit (MSU) instruments for 1979‐97. The various analyses are performed using monthly mean temperatures from a near‐globally distributed network of 87 radiosonde stations. The severity of instrument-related problems, which varies markedly by geographic region, was found, in general, to increase from the lower troposphere to the lower stratosphere, although surface data were found to be as problematic as data from the stratosphere. Except for the surface, there is a tendency for changes in instruments to artificially lower temperature readings with time, so that adjusting the data to account for this results in increased tropospheric warming and decreased stratospheric cooling. Furthermore, the adjustments tend to enhance warming in the upper troposphere more than in the lower troposphere; such sensitivity may have implications for ‘‘fingerprint’’ assessments of climate change. However, the most sensitive part of the vertical profile with regard to its shape was near the surface, particularly at regional scales. In particular, the lower-tropospheric lapse rate was found to be especially sensitive to adjustment as well as spatial sampling. In the lower stratosphere, instrument-related biases were found to artificially inflate latitudinal differences, leading to statistically significantly more cooling in the Tropics than elsewhere. After adjustment there were no significant differences between the latitude zones.

Applicability of T-S algorithms to the Canary Islands region

The high cost of oceanographic cruises often makes it advisable to use opportunity vessels for simple measurements, such as determining the temperature of the water column with expandable bathythermographs (XBT). In this work we examine the goodness and reliability of a method aimed at obtaining the maximum possible information from XBT data, and we apply it to the Canary Islands region. It consists in calculating analytic relations between temperature and salinity from historical conductivity-temperature-depth (CTD) data for the region, which are then used to hindcast/forecast the salinity and density distribution, as well as the distribution of other inferred quantities such as velocity. A hindcasting is carried out using direct independent temperature measurements obtained from a hydrographic cruise south of the island of Gran Canaria. At depths greater than 100-150 m the results show good agreement with the calculations obtained from CTD in situ data.

A SVAT scheme describing energy and CO 2 fluxes for multi-component vegetation: calibration and test for a Sahelian savannah

A soil vegetation atmosphere transfer scheme (SVAT), describing the fluxes of heat, water vapour and CO 2 between a multi-component vegetated land surface and the atmosphere, has been developed. The SVAT has been calibrated and tested using 30 days of micrometeorological and physiological measurements collected over a sparse savannah in the Sahel. The model explicitly represents the four major functional components of the savannah: shrubs (C 3 photosynthesis), grasses (C 4), herbs (C 3) and bare soil. The leaf conductance model for the shrub, grass and herb components was calibrated against porometry measurements made in the field. The performance of the SVAT was tested against independent surface flux and temperature measurements. Agreement between the model predictions and measurements of the total net radiation, sensible and latent heat fluxes, net CO 2 exchange and surface temperatures was good: in all cases at least 80% of the variance in the measurements was explained by the model. Separate flux and surface temperature predictions for the four surface components were satisfactory, although complete verification was difficult as data were lacking for some variables. Predicted water use efficiency (WUE) of the vegetation showed a strong, non-linear dependence on vapour pressure deficit, especially for the bushes and the grasses. WUE for the grasses was about three times as large as the values found for the bushes and herbs. A SVAT model like this can be employed to address the possible effects of CO 2 enrichment and climate change on the competitive balance between different species in a plant community or in research concerning productivity and water use efficiency in mixed crops, such as agroforestry systems.

Challenges and current status in 300 mm rapid thermal processing

Rapid Thermal Processing (RTP) will be indispensable to meet the process requirements of future device and integrated circuit (IC) generations. The paper reviews several approaches to manage the challenges of single-wafer 300 mm heat treatment, including the most important issues in RTP system technology: temperature measurement and accuracy, fast ramp capability, process repeatability, ultra-shallow junction formation and process uniformity for various applications in concurrent IC manufacturing. The paper also focuses on the substantial improvement of key system features. The implementation of a new lamp intensity modulation-based and emissivity independent temperature measurement technique yields a measurement uncertainty of ±1.5°C within an emissivity range from 0.2 to 0.8 for key process applications.

A linear multisensor for temperature and magnetic field based on diode structure

A new type linear silicon multisensor using the functional principle for simultaneous and independent measurement of temperature and magnetic field is suggested and investigated experimentally in wide temperature range 77 K≤ T≤393 K. The structure is a differential microdiode with strip geometry. The temperature output signal is the anode–cathode voltage at a constant supply current, which is linear in the range 77 K≤ T≤393 K, but the magnetosensitive one is a differential current between both base contacts. A strong magnetic field up to 1.5 T at T=300 K does not influence the selected thermometric signal.

Wafer emissivity independent temperature measurements

A study on the techniques to yield wafer emissivity independent temperature measurements in rapid thermal processing has been presented. This study focuses on the Steag-AST Electronik approach to enhance wafer emissivity by using the Hotliner*. The Hotliner comprises of a heavily doped p-Si substrate sandwiched with Si3N4/SiO2 from both sides. Experimental measurements on the optical properties of the Hotliner using a spectral emissometer operating in the wavelength range of 1–20 µm are presented here. Results of the simulation of the experimental data using the MIT/SEMATECH Multi-Rad model are discussed.

Recent observations of high-frequency acoustic wave propagation in the Delaware Bay

Broadband acoustic propagation measurements, as well as complementary environmental measurements including CTD, ADCP, and wind speed, have been conducted in the Delaware Bay during March and September, 1997. With the data from these complete experiments, acoustic pulse travel time and intensity are related to the sound-speed fluctuations in the water column, the sea-surface profile, and the bottom roughness. The direct arrival between acoustic source and receiver contains information about ocean current and temperature, while the arrival corresponding to a single surface bounce contains additional information about the sea-surface roughness. Independent measurements of temperature and current allow the sorting of acoustic fluctuations due to ocean volume fluctuations from those due to sea-surface fluctuations. Coherence of the broadband acoustic signals is calculated from the observed data and is found to be correlated with the environmental parameters.

An Improved Coupled Model for ENSO Prediction and Implications for Ocean Initialization. Part I: The Ocean Data Assimilation System

An improved forecast system has been developed for El Niño–Southern Oscillation (ENSO) prediction at the National Centers for Environmental Prediction. Improvements have been made both to the ocean data assimilation system and to the coupled ocean–atmosphere forecast model. In Part I of a two-part paper the authors describe the new assimilation system. The important changes are 1) the incorporation of vertical variation in the first-guess error variance that concentrates temperature corrections in the thermocline and 2) the overall reduction in the magnitude of the estimated first-guess error. The new system was used to produce a set of retrospective ocean analyses for 1980–95. The new analyses are less noisy than their earlier counterparts and compare more favorably with independent measurements of temperature, currents, and sea surface height variability. Part II of this work presents the results of using these analyses to initialize the coupled forecast model for ENSO prediction.

Advances in Rtp Temperature Measurement and Control

ABSTRACTThis paper reviews work to develop and improve the temperature measurement and control technology of a commercial rapid thermal processing (RTP) system. A description of the main features of this system is given, which includes a concentric multi-zone lamp heating source, multi-point temperature measurement system and real time wafer temperature control. Innovations in RTP optical thermometry are described which resulted in improved low temperature performance, a real time spectral emissivity measurement tool which enables emissivity independent temperature measurement and an improved temperature calibration capability. The multi-input multi-output (MIMO) optimal wafer temperature control methodology is discussed. Process results demonstrating an equivalent process temperature performance of 4°C, 3-sigma, all-points-all-wafers will be presented.

Simultaneous measurement of strain and temperature using the first- and second-order diffraction wavelengths of Bragg gratings

A method of discriminating between temperature and strain effects in fibre sensing using a conventionally written, in-fibre Bragg grating is presented. The technique uses wavelength information from the first and second diffraction orders of the grating element to determine the wavelength dependent strain and temperature coefficients, from which independent temperature and strain measurements can be made. The authors present results that validate this matrix inversion technique and quantify the strain and temperature errors which can arise for a given uncertainty in the measurement of the reflected wavelength.

Optimization of the Ast Hot Liner™ for Sub-Micron Production

ABSTRACTIn an effort to develop an emissivity independent temperature measurement technique for the AST Rapid Thermal Processor (RTP), AST has conceived of the Hot Liner™. The Hot Liner is a silicon nitride coated silicon wafer which is permanently installed in the process chamber, immediately below the wafer. The pyrometer, which is calibrated to a production wafer, views the constant emissivity Hot Liner to produce repeatable temperatures on product wafers regardless of their backside emissivity.Given the repeatability of the Hot Liner, the wafer temperature uniformity must then be optimized in order to achieve 0.25μm capable processing. AST has developed a methodology which incorporates process monitors (ion implanted test wafers) to establish process uniformity in addition to multiple thermocouple wafers to verify across wafer temperature uniformity. The process monitors are used to separately optimize the ramp and steady state steps in the production recipe.Utilizing the AST methodology to optimize processing with the Hot Liner has allowed AMD to significantly improve its RTA processing. The Hot Liner greatly decreases backside and pyrometer effects which yields limited wafer to wafer variation (< 5C, 3σ). In combination with the optimization process this results in excellent within wafer uniformity (< 3C, 3σ).

Polarimetric Er^3+-doped fiber distributed-feedback laser sensor for differential pressure and force measurements

We propose and demonstrate a polarimetric Er(3+) -doped fiber distributed-feedback laser sensor in which a force applied transversely along the fiber laser induces a birefringence that gives rise to a change in the beat frequency between the two orthogonally polarized laser modes. We measure a sensitivity of ~9.6 GHzysNymmd, a wide dynamic range with stable two-mode operation for frequency separations up to 50 GHz, and high sensor resolution owing to the narrow beat frequency bandwidth of <10 kHz. The temperature sensitivity is dominated by the temperature dependence of the inherent birefringence, which was measured to be -130 kHz/ degrees C. The sensor permits independent pressure-force and temperature measurements.

Jet impingement drying of a moist porous solid

This paper investigates the thermal characteristics of a continuous industrial drying process for semi-porous textile composites. The conservation of mass, momentum and energy are written for a partially saturate porous fiber layer attached to a solid-backing layer. The numerical solution of the one-dimensional and transient conservation equations provides the temperature, volumetric saturation and gas phase pressure distributions in the moist porous solid and the temperature distribution in the solid-backing layer. During the wet region drying period, continuous liquid exists in the pore space, the moisture transport within the solid is described by the Darcy form of the momentum equation. The moisture transport in the sorption region is described by a bound liquid diffusion and gas phase transport. For the jet impingement type dryer, it is assumed that the penetration of the flow field into the porous solid is small (assumed valid due to the presence of the solid backing). The enhanced transport coefficients at the drying surface are estimated with the use of the Kolmogoroff theory of isotropic turbulence. This theory provides correlations for the heat and mass transfer coefficients from the fluid properties and the turbulent energy dissipation rate in the fluid. The model results of the continuous industrial drying process are compared to independent experimental temperature and global moisture content measurements taken in an operational industrial dryer. From the model analysis and experimental data, the heat flux conditions at the drying surface dictate the manner in which the solid is dried. The heat transfer coefficients considered are in the range of 20–130 W m −2K −1 and necessarily affect the manner in which moisture transport occurs within the solid. It is seen that the lower heat transfer coefficients more accurately represent the internal transport phenomena occurring during the drying process and the heating of the solid. The transport coefficients are compared to previously obtained empirical results.

Measurement of time varying temperature fields using visible imaging CCD cameras

A method for measuring time-varying surface temperature distributions using high frame rate visible imaging CCD cameras is described. The technique is based on an ad hoc model relating measured radiance to local surface temperature. This approach is based on the fairly non-restrictive assumptions that atmospheric scattering and absorption, and secondary emission and reflection are negligible. In order to assess performance, both concurrent and non-concurrent calibration and measurement, performed under dynamic thermal conditions, are examined. It is found that measurement accuracy is comparable to the theoretical accuracy predicted for infrared-based systems. In addition, performance tests indicate that in our experimental system, real-time calibration can be achieved while real-time whole-field temperature measurements require relatively course spatial resolution. The principal advantages of the proposed method are its simplicity and low cost. In addition, since independent temperature measurements are used for calibration, emissivity remains unspecified, so that a potentially significant source of error is eliminated.