| 1. |
- Feuk, Henrik, et al.
(författare)
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Investigating photomultiplier tube nonlinearities in high-speed phosphor thermometry using light emitting diode simulated decay curves
- 2021
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 92:12
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Tidskriftsartikel (refereegranskat)abstract
- Photomultiplier tube (PMT) nonlinearities relevant for single shot high-speed lifetime phosphor thermometry were investigated by simulating decay curves with a light emitting diode (LED) at repetition rates between 1 Hz and 10 kHz. The PMT gain, LED decay time, and background radiant flux were also varied to investigate their impact on the measured decay time error. Errors in the measured decay time due to nonlinear PMT performance lead to temperature measurement errors; therefore, having the measured decay time sensitive to only phosphor temperature is highly valuable for more reliable temperature measurements. Photocathode bleaching had a significant impact on the signal level linearity for PMTs with excitation frequency in the kHz regime but had a smaller impact on the decay time error. Space charge effects were most noticeable at high radiant flux levels and high repetition rates. Strong background radiant flux may lead to decay time errors, and a gateable photocathode could be an effective method to reduce decay time errors. The best decay time measurement configuration to maximize precision without sacrificing accuracy is to use PMT gain in the recommended range and the highest radiant flux where the PMT response is still linear. The degree of nonlinearity in the PMT response is partly detector dependent; therefore, the results in this work may differ among detectors; however, the analysis presented in this work provides guidelines for improving the temperature accuracy of kHz lifetime phosphor thermometry measurements.
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| 2. |
- Joo, Peter, et al.
(författare)
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Experimental apparatus with full optical access for combustion experiments with laminar flames from a single circular nozzle at elevated pressures.
- 2015
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:3
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Tidskriftsartikel (refereegranskat)abstract
- The design and features of a high pressure chamber and burner that is suitable for combustion experiments at elevated pressures are presented. The high pressure combustion apparatus utilizes a high pressure burner that is comprised of a chamber burner module and an easily accessible interchangeable burner module to add to its flexibility. The burner is well suited to study both premixed and non-premixed flames. The optical access to the chamber is provided through four viewports for direct visual observations and optical-based diagnostic techniques. Auxiliary features include numerous access ports and electrical connections and as a result, the combustion apparatus is also suitable to work with plasmas and liquid fuels. Images of methane flames at elevated pressures up to 25 atm and preliminary results of optical-based measurements demonstrate the suitability of the high pressure experimental apparatus for combustion experiments.
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| 3. |
- Knappe, Christoph, et al.
(författare)
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Comparison of photo detectors and operating conditions for decay time determination in phosphor thermometry
- 2012
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:9
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Tidskriftsartikel (refereegranskat)abstract
- 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 (CdWO4). 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 CdWO4 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. © 2012 American Institute of Physics.
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| 4. |
- Knappe, Christoph, et al.
(författare)
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Investigation and compensation of the nonlinear response in photomultiplier tubes for quantitative single-shot measurements.
- 2012
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:3
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Tidskriftsartikel (refereegranskat)abstract
- A concept for time-sensitive optical detectors is described that shows how to confirm whether the detection device is operating in the linear response regime. By evaluating the recorded time decay of a thermographic phosphor, even weak saturation effects far from obvious situations can be identified and further related to either optical or electrical saturation. The concept has been validated by running a PMT detector close to saturation and exposing it to the optical signal decay of two different thermographic phosphors, La(2)O(2)S:Eu and CdWO(4). It was confirmed that short but intense light exposures at the beginning of an individual time decay influence the detector response for the rest of the decaying signal including temporal areas, where the anode current has dropped well below the manufacturer specified current limit. Such situations are common when applying, e.g., phosphor thermometry where it is necessary to retrieve the full decay curve from a single-shot event, i.e., standard techniques based on single-photon counting are omitted. Finally, means of compensation are introduced in order to facilitate the retrieval of useful information from the measurement data when operation in the non-linear response regime is inevitable.
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| 5. |
- Li, Zhongshan, et al.
(författare)
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Applications of a single-longitudinal-mode alexandrite laser for diagnostics of parameters of combustion interest
- 2004
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 75:10, s. 3208-3215
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Tidskriftsartikel (refereegranskat)abstract
- We report on the applications of a single-longitudinal-mode (SLM) pulsed alexandrite laser system for diagnostics of parameters of flow/combustion interest. The laser system is characterized by its narrow linewidth, high peak power, and broad tunablity. The absolute frequency of the laser output was monitored by a wavelength diagnostic system, which included a high-resolution confocal etalon and a molecular iodine laser-induced fluorescence (LIF) detection system. Different nonlinear frequency conversion schemes were used to cover a large frequency range from the infrared to the deep UV. The versatility of the laser system for flow/combustion diagnostics is demonstrated in three applications, namely filtered Rayleigh scattering, high-resolution Doppler-free two-photon LIF of CO, and infrared LIF and polarization spectroscopy of CO2. The potential impacts of using this SLM laser system in laser flow/combustion diagnostic applications are discussed. (C) 2004 American Institute of Physics.
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| 6. |
- Olofsson, Jimmy, et al.
(författare)
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Development of high temporally and spatially (three-dimensional) resolved formaldehyde measurements in combustion environments
- 2006
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 77:1
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Tidskriftsartikel (refereegranskat)abstract
- In the present article a multi-YAG laser cluster and a framing camera have been applied for ultrahigh framing rate and three-dimensional measurements of formaldehyde distribution in flames and engines. The measurement technique utilizes a laser/detection system which has been adopted for the generation of eight laser pulses at 355 nm. By combining these lasers with a framing camera, short movies showing the formaldehyde distributions in combustion phenomena can be recorded, by means of planar laser-induced fluorescence. The technique is successfully demonstrated in a laboratory flame as well as in an engine. In addition to the temporally resolved experiments also three-dimensional measurements are performed by sweeping the eight generated laser sheets across the flame by the use of a fast scanning mirror. By proper triggering of the laser sweep and the detector a three-dimensional image showing the formaldehyde distribution in the flame can be created, which is also demonstrated. (c) 2006 American Institute of Physics.
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| 7. |
- Weng, Wubin, et al.
(författare)
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A novel multi-jet burner for hot flue gases of wide range of temperatures and compositions for optical diagnostics of solid fuels gasification/combustion
- 2017
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 88:4
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Tidskriftsartikel (refereegranskat)abstract
- A novel multi-jet burner was built to provide one-dimensional laminar flat flames with a wide range of variable parameters for multipurpose quantitative optical measurements. The burner is characterized by two independent plenum chambers, one supporting a matrix of 181 laminar jet flames and the other supporting a co-flow from a perforated plate with small holes evenly distributed among the jets. A uniform rectangular burned gas region of 70 mm × 40 mm can be generated, with a wide range of temperatures and equivalence ratios by controlling independently the gas supplies to the two plenum chambers. The temperature of the hot gas can be adjusted from 1000 K to 2000 K with different flame conditions. The burner is designed to seed additives in gas or liquid phase to study homogeneous reactions. The large uniform region can be used to burn solid fuels and study heterogeneous reactions. The temperature was measured using two-line atomic fluorescence thermometry and the temperature profile at a given height above the burner was found to be flat. Different types of optical diagnostic techniques, such as line of sight absorption or laser-induced fluorescence, can be easily applied in the burner, and as examples, two typical measurements concerning biomass combustion are demonstrated.
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| 8. |
- Whiddon, Ronald, et al.
(författare)
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Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry.
- 2015
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:9
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Tidskriftsartikel (refereegranskat)abstract
- Tri-methyl-indium (TMI) is used as an indium transport molecule to introduce indium atoms to reactive hot gas flows/combustion environments for spectroscopic diagnostics. A seeding system was constructed to allow the addition of an inert TMI laden carrier gas into an air/fuel mixture burning consequently on a burner. The amount of the seeded TMI in the carrier gas can be readily varied by controlling the vapor pressure through the temperature of the container. The seeding process was calibrated using the fluorescent emission intensity from the indium 6(2)S1/2 → 5(2)P1/2 and 6(2)S1/2 → 5(2)P3/2 transitions as a function of the calculated TMI seeding concentration over a range of 2-45 ppm. The response was found to be linear over the range 3-22.5 ppm; at concentrations above 25 ppm there is a loss of linearity attributable to self-absorption or loss of saturation of TMI vapor pressure in the carrier gas flow. When TMI was introduced into a post-combustion environment via an inert carrier gas, molecular transition from InH and InOH radicals were observed in the flame emission spectrum. Combined laser-induced fluorescence and absorption spectroscopy were applied to detect indium atoms in the TMI seeded flame and the measured atomic indium concentration was found to be at the ppm level. This method of seeding organometallic vapor like TMI to a reactive gas flow demonstrates the feasibility for quantitative spectroscopic investigations that may be applicable in various fields, e.g., chemical vapor deposition applications or temperature measurement in flames with two-line atomic fluorescence.
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| 9. |
- Zetterberg, Johan, et al.
(författare)
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An in situ set up for the detection of CO(2) from catalytic CO oxidation by using planar laser-induced fluorescence.
- 2012
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:5
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Tidskriftsartikel (refereegranskat)abstract
- We report the first experiment carried out on an in situ setup, which allows for detection of CO(2) from catalytic CO oxidation close to a model catalyst under realistic reaction conditions by the means of planar laser-induced fluorescence (PLIF) in the mid-infrared spectral range. The onset of the catalytic reaction as a function of temperature was followed by PLIF in a steady state flow reactor. After taking into account the self-absorption of CO(2), a good agreement between the detected CO(2) fluorescence signal and the CO(2) mass spectrometry signal was shown. The observed difference to previously measured onset temperatures for the catalytic ignition is discussed and the potential impact of IR-PLIF as a detection technique in catalysis is outlined.
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