Comparison of photo detectors and operating conditions for decay time determination in phosphor thermometry

Abstract

M. (2012). Comparison of photo detectors and operating conditions for decay time determination in phosphor thermometry. Review of Scientific Instruments, 83(9), [094901]. DOI: 10.1063/1.4746990 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal This work compares the extent of linear response regions from standard time-resolving optical detectors for phosphor thermometry. Different types of photomultipliers (ordinary and time-gated) as well as an avalanche photodiode were tested and compared using the phosphorescence decay time of cadmium tungstate (CdWO 4 ). Effects originating from incipient detector saturation are revealed as a change in evaluated phosphorescence decay time, which was found to be a more sensitive measure for saturation than the conventional signal strength comparison between in-and output. Since the decay time of thermographic phosphors is used for temperature determination systematic temperature errors in the order of several tens of Kelvins may be introduced. Saturation from the initial intensity is isolated from temporally developed saturation by varying the CdWO 4 decay time over the microsecond to nanosecond range, resultant of varying the temperature from 290 to 580 K. A detector mapping procedure is developed in order to identify linear response regions where the decay-to-temperature evaluations are unbiased. In addition, this mapping procedure generates a library of the degree of distortion for operating points outside of linear response regions. Signals collected in the partly saturated regime can thus be corrected to their unbiased value using this library, extending the usable detector operating range significantly.

Single fiber temperature probe configuration using anti-Stokes luminescence from Cr:GdAlO3

“…This Raman scattering (along with any prompt fluorescence) does not persist beyond the short laser excitation pulse (typically about 10 ns duration) and therefore precedes most of the phosphor sensor decay curve. However, this high signal intensity spike distorts the ensuing decay as either one or both of the detector (such as a photomultiplier tube) and electronic measurement instrument (such as an oscilloscope) recover from the spike [26][27][28]. With no filtering in a single fiber probe configuration to remove the background light intensity generated in the laser delivery fiber and probe, the initial spike can significantly distort the measured phosphor emission decay for several microseconds.…”

Development of an automatic routine for calibration of thermographic phosphors

“…A Hamamatsu H11526-20-NF photomultiplier tube was used as the detector. According to recent investigations by the authors, this PMT type showed superior signal linearity compared to other detector types [13]. A control voltage of 0.339 V set the photomultiplier gain constant throughout the entire experiment.…”

“…A well-constructed calibration curve is important for an accurate thermographic phosphor temperature determination. The process of obtaining a phosphor calibration curve can be tedious and accompanied with effects such as detector nonlinearity [13,14]. Despite the importance of the calibration, no major development has occurred or been reported for the method by which the temperature calibration is achieved.…”

A First Application of Thermographic Phosphors in a Marine Two-Stroke Diesel Engine for Surface Temperature Measurement

“…Severe signal distortions can occur to the measured signal if the detector is operating in its nonlinear region. The importance of detector linearity in phosphor thermometry was characterized and reported by Knappe et al [25,26]. The studies showed that photodetectors can severely distort the shape of the exponentially decaying signals.…”

“…By testing an array of different photodetectors, the authors have identified a detector that provides superior linearity response among the tested photodetectors [26]. This detector is the Hamamatsu H11526-20-NF.…”