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Feb 2013

Volume 84, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 84, 021101 (2013); http://dx.doi.org/10.1063/1.4789314 (14 pages)

Alexey Goncharov

Typical permanent magnet electrostatic plasma lens, characteristically about 15 cm long and 10 cm inner diameter. The magnets are shown in black between grey spacers. A set of cylindrical ring electrodes are located within the magnetic field region, with field lines connecting ring electrode pairs symmetrically about the lens midplane.

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back to top Thermometry; Thermal Diffusivity; Acoustics; Photothermal and Photoacoustic

Frequency domain analysis of spreading-constriction thermal impedance

Francesco Casalegno, Andrea De Marchi, and Valter Giaretto

Rev. Sci. Instrum. 84, 024901 (2013); http://dx.doi.org/10.1063/1.4789765 (3 pages)

Online Publication Date: 5 February 2013

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Spreading-constriction effects are analyzed in the frequency domain. The existence of a half-pole altering the steady state solution at high frequencies is pointed out. Application to the case of thermoelectric devices allows direct comparison with experimental data because thermal quantities can be measured as electrical signals at the very spot where spreading takes place. Good agreement with theory is shown here for a thermoelectric device in which the particular constriction geometry enhances its effect, making easily observable the difference between frequency domain and the steady state approaches.
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85.80.Fi Thermoelectric devices
07.20.-n Thermal instruments and apparatus

Thermocouple error correction for measuring the flame temperature with determination of emissivity and heat transfer coefficient

V. Hindasageri, R. P. Vedula, and S. V. Prabhu

Rev. Sci. Instrum. 84, 024902 (2013); http://dx.doi.org/10.1063/1.4790471 (11 pages)

Online Publication Date: 11 February 2013

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Temperature measurement by thermocouples is prone to errors due to conduction and radiation losses and therefore has to be corrected for precise measurement. The temperature dependent emissivity of the thermocouple wires is measured by the use of thermal infrared camera. The measured emissivities are found to be 20%–40% lower than the theoretical values predicted from theory of electromagnetism. A transient technique is employed for finding the heat transfer coefficients for the lead wire and the bead of the thermocouple. This method does not require the data of thermal properties and velocity of the burnt gases. The heat transfer coefficients obtained from the present method have an average deviation of 20% from the available heat transfer correlations in literature for non-reacting convective flow over cylinders and spheres. The parametric study of thermocouple error using the numerical code confirmed the existence of a minimum wire length beyond which the conduction loss is a constant minimal. Temperature of premixed methane-air flames stabilised on 16 mm diameter tube burner is measured by three B-type thermocouples of wire diameters: 0.15 mm, 0.30 mm, and 0.60 mm. The measurements are made at three distances from the burner tip (thermocouple tip to burner tip/burner diameter = 2, 4, and 6) at an equivalence ratio of 1 for the tube Reynolds number varying from 1000 to 2200. These measured flame temperatures are corrected by the present numerical procedure, the multi-element method, and the extrapolation method. The flame temperatures estimated by the two-element method and extrapolation method deviate from numerical results within 2.5% and 4%, respectively.
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07.20.Dt Thermometers
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Photothermal model fitting in the complex plane for thermal properties determination in solids

M. A. Zambrano-Arjona, F. Peñuñuri, M. Acosta, I. Riech, R. A. Medina-Esquivel, P. Martínez-Torres, and J. J. Alvarado-Gil

Rev. Sci. Instrum. 84, 024903 (2013); http://dx.doi.org/10.1063/1.4790433 (5 pages)

Online Publication Date: 13 February 2013

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Thermal properties of solids are obtained by fitting the exact complex photothermal model to the normalized photoacoustic (PA) signal in the front configuration. Simple closed-form expressions for the amplitude and phase are presented in all frequency ranges. In photoacoustic it has been common practice to assume that all the absorptions of radiation take place in the sample. However, in order to obtain the accurate thermal properties it is necessary to consider the PA signal contributions produced at the cell walls. Such contributions were considered in our study. To demonstrate the usefulness of the proposed methodology, commercial stainless steel layers AISI 302 were analyzed. It is shown that using our approach the obtained thermal diffusivity and effusivity were in good agreement with those reported in the literature. Also, a detailed procedure for the calculation of the standard error in the thermal properties is discussed.
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78.20.nb Photothermal effects
62.65.+k Acoustical properties of solids
78.20.Pa Photoacoustic effects

A method of reducing background radiance for emissivity-compensated radiation thermometry of silicon wafers

T. Iuchi, Y. Toyoda, and T. Seo

Rev. Sci. Instrum. 84, 024904 (2013); http://dx.doi.org/10.1063/1.4791793 (7 pages)

Online Publication Date: 20 February 2013

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We studied the spectral and directional emissivities of silicon wafers using an optical polarization technique. Based on simulation and experimental results, we developed two radiation thermometry methods for silicon wafers: one is based on the polarized emissivity-invariant condition and the other is based on the relationship between the ratio of the p- and s-polarized radiance and the polarized emissivity. These methods can be performed at temperatures above 600 °C and over a wide wavelength range (0.9–4.8 μm), irrespective of the dielectric film thickness and the substrate resistivity, which depends on the dopant concentration. The temperature measurements were estimated to have expanded uncertainties (k = 2) of less than 5 °C. With a view to practically applying these methods, we investigated a method to reduce the intense background radiance produced by high-intensity heating lamps. We found that the background radiance can be greatly reduced by using a radiometer that is sensitive to wavelengths of 4.5 or 4.8 μm and suitable geometrical arrangements of a quartz plate. This opens up the possibility of using the two proposed radiation thermometry methods in practical applications.
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07.20.Dt Thermometers
77.55.-g Dielectric thin films
07.60.Dq Photometers, radiometers, and colorimeters
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