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James Filla  - - - 
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Zeeshan Ahmed

41 shared publications

National Institute of Standards and Technology, 100 Bureau Dr. Gaithersburg, Maryland 20899

John Quintavalle

3 shared publications

Innovations and Solutions Division, National Institute of Standards and Technology, Gaithersburg, MD 20899

L.F. Goodrich

1 shared publications

Department of Physics, University of Colorado, Boulder, CO 80309

N. Cheggour

1 shared publications

Department of Physics, University of Colorado, Boulder, CO 80309

T.C. Stauffer

1 shared publications

National Institute of Standards and Technology, Boulder, CO 80305

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Publication Record
Distribution of Articles published per year 
(2013 - 2016)
Total number of journals
published in
 
2
 
Publications
Article 0 Reads 1 Citation Fiber Bragg Grating Based Thermometry Zeeshan Ahmed, James Filla, William Guthrie, John Quintavall... Published: 12 May 2016
NCSLI Measure, doi: 10.1080/19315775.2015.11721744
DOI See at publisher website PubMed View at PubMed ABS Show/hide abstract
In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in hermetically sealed dry Argon environment, FBG devices show a quadratic dependence on temperature with expanded uncertainties (k=2) of ≈500 mK. Our measurements indicate that the combined measurement uncertainty is dominated by uncertainty in determining peak center fitting and thermal ageing of polyimide coated fibers.
PREPRINT 0 Reads 0 Citations Fiber Bragg Grating Based Thermometry Zeeshan Ahmed, James Filla, William Guthrie, John Quintavall... Published: 24 March 2016
ABS Show/hide abstract
In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature range of 233 K to 393 K. We demonstrate, in a hermetically sealed dry Argon environment, that FBG devices show a quadratic dependence on temperature with expanded uncertainties (k = 2) of ~500 mK. Our measurements indicate that the combined measurement uncertainty is dominated by uncertainty in determining the peak center fitting and by thermal aging of polyimide coated fibers.
PREPRINT 0 Reads 0 Citations Developing Microwave Photonic Temperature Sensors Arec Jamgochian, John Quintavalle, Alejandra Torres-Diaz, Ja... Published: 06 August 2015
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In recent years there has been considerable interest in exploiting the temperature dependence of sapphire whispering gallery mode frequency to develop a mechanically stable, high accuracy temperature sensor. Disk-resonator-based devices have been demonstrated to measure temperature with .01 K or better accuracy in the temperature range of 273 K to 373 K. Here we have utilized automated data acquisition and processing to rapidly evaluate a mechanically-stabilized sapphire whispering gallery mode resonator based on a hollow cylinder configuration.
Article 0 Reads 2 Citations Kiloampere, Variable-Temperature, Critical-Current Measurements of High-Field Superconductors L.F. Goodrich, N. Cheggour, T.C. Stauffer, B.J. Filla, X.F. ... Published: 19 August 2013
Journal of Research of the National Institute of Standards and Technology, doi: 10.6028/jres.118.015
DOI See at publisher website PubMed View at PubMed ABS Show/hide abstract
We review variable-temperature, transport critical-current (Ic) measurements made on commercial superconductors over a range of critical currents from less than 0.1 A to about 1 kA. We have developed and used a number of systems to make these measurements over the last 15 years. Two exemplary variable-temperature systems with coil sample geometries will be described: a probe that is only variable-temperature and a probe that is variable-temperature and variable-strain. The most significant challenge for these measurements is temperature stability, since large amounts of heat can be generated by the flow of high current through the resistive sample fixture. Therefore, a significant portion of this review is focused on the reduction of temperature errors to less than ±0.05 K in such measurements. A key feature of our system is a pre-regulator that converts a flow of liquid helium to gas and heats the gas to a temperature close to the target sample temperature. The pre-regulator is not in close proximity to the sample and it is controlled independently of the sample temperature. This allows us to independently control the total cooling power, and thereby fine tune the sample cooling power at any sample temperature. The same general temperature-control philosophy is used in all of our variable-temperature systems, but the addition of another variable, such as strain, forces compromises in design and results in some differences in operation and protocol. These aspects are analyzed to assess the extent to which the protocols for our systems might be generalized to other systems at other laboratories. Our approach to variable-temperature measurements is also placed in the general context of measurement-system design, and the perceived advantages and disadvantages of design choices are presented. To verify the accuracy of the variable-temperature measurements, we compared critical-current values obtained on a specimen immersed in liquid helium (“liquid” or Ic liq) at 5 K to those measured on the same specimen in flowing helium gas (“gas” or Ic gas) at the same temperature. These comparisons indicate the temperature control is effective over the superconducting wire length between the voltage taps, and this condition is valid for all types of sample investigated, including Nb-Ti, Nb3Sn, and MgB2 wires. The liquid/gas comparisons are used to study the variable-temperature measurement protocol that was necessary to obtain the “correct” critical current, which was assumed to be the Ic liq. We also calibrated the magnetoresistance effect of resistive thermometers for temperatures from 4 K to 35 K and magnetic fields from 0 T to 16 T. This calibration reduces systematic errors in the variable-temperature data, but it does not affect the liquid/gas comparison since the same thermometers are used in both cases.
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