| 1. |
- Abou Nada, Fahd Jouda, et al.
(författare)
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Improved measurement precision in decay time‑based phosphor thermometry
- 2016
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 1432-0649 .- 0946-2171. ; 122
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Tidskriftsartikel (refereegranskat)abstract
- This study comprises a continuation of the previous efforts of the authors to characterize different sources of errors in phosphor thermometry based on the determination of luminescence decays from thermographic phosphors. Whereas earlier investigations focused on point detectors utilizing different sensor technology, this work presents a comparison of four PMTs that are identical in terms of their product type. These detectors are supposedly identical, but the investigations revealed that their response is strictly individual. This study also shows a linear excitation energy dependence for the decay time of cadmium tungstate (CdWO4), the phosphor being used in this work. In addition, the potential influence of the intense and short fluorescence peak preceding the weaker and longer exponential decay in some phosphor materials, was investigated using the electrical signal gating capability of the PMT. Finally, the evaluated decay time also appeared to be affected by the oscilloscope settings used when recording the phosphorescence signals. The presented results indicate that all operating parameters from the calibration measurement need to be rigorously reproduced in order to avoid systematic temperature errors in phosphor thermometry experiments that are based on reproducible measurements of the decay time. These results should be of more general interest also outside the phosphor community as the findings, presented herein, in principal concern all kinds of measurements that are dependent on reproducible measurements of signal shapes or time-transients.
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| 2. |
- Aurand, Bastian, et al.
(författare)
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Reduction of X-ray generation in high-intensity laser ion acceleration
- 2015
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 118:2, s. 247-251
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report on measurements of bremsstrahlung in laser ion acceleration experiments from ultra-thin, polymer-based target foils. The influence of laser polarization on the generated radiation, the maximum achievable proton energy and the total proton number is investigated. A clear benefit in terms of radiation reduction by the use of circular polarized light can be observed. At the same time, the total number of accelerated protons was increased.
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| 3. |
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| 4. |
- Borggren, Jesper, et al.
(författare)
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Diode laser-based thermometry using two-line atomic fluorescence of indium and gallium
- 2017
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Ingår i: Applied Physics B: Lasers and Optics. - : Springer Science and Business Media LLC. - 0946-2171. ; 123:12
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Tidskriftsartikel (refereegranskat)abstract
- A robust and relatively compact calibration-free thermometric technique using diode lasers two-line atomic fluorescence (TLAF) for reactive flows at atmospheric pressures is investigated. TLAF temperature measurements were conducted using indium and, for the first time, gallium atoms as temperature markers. The temperature was measured in a multi-jet burner running methane/air flames providing variable temperatures ranging from 1600 to 2000 K. Indium and gallium were found to provide a similar accuracy of ~ 2.7% and precision of ~ 1% over the measured temperature range. The reliability of the TLAF thermometry was further tested by performing simultaneous rotational CARS measurements in the same experiments.
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| 5. |
- Borggren, Jesper, et al.
(författare)
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Temperature imaging in low-pressure flames using diode laser two-line atomic fluorescence employing a novel indium seeding technique
- 2016
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 122:3
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Tidskriftsartikel (refereegranskat)abstract
- The use of diode lasers for spatially resolved temperature imaging is demonstrated in low-pressure premixed methane–air flames using two-line atomic fluorescence of seeded indium atoms. This work features the advantages of using compact diode lasers as the excitation sources with the benefits of two-dimensional planar imaging, which is normally only performed with high-power pulsed lasers. A versatile and reliable seeding technique with minimal impact on flame properties is used to introduce indium atoms into the combustion environment for a wide range of flame equivalence ratios. A spatial resolution of around 210 µm for this calibration-free thermometry technique is achieved for three equivalence ratios at a pressure of 50 mbar in a laminar flat flame.
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| 6. |
- Coetzee, Riaan Stuart, et al.
(författare)
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Narrowband, tunable, 2 A mu m optical parametric master-oscillator power amplifier with large-aperture periodically poled Rb:KTP
- 2018
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Ingår i: Applied physics. B, Lasers and optics (Print). - : SPRINGER. - 0946-2171 .- 1432-0649. ; 124:6
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Tidskriftsartikel (refereegranskat)abstract
- A high-energy, ns, narrow-linewidth optical parametric oscillator and amplifier system based on large-aperture periodically poled Rb:KTP is presented. The 2 A mu m seed source is a singly resonant OPO locked with a transversely chirped volume Bragg grating, allowing a wavelength tuning of 21 nm and output linewidth of 0.56 nm. A maximum output energy of 52 mJ and conversion efficiency of 36% was obtained from the amplifier for a pump energy of 140 mJ. The high-energy and the robust and narrow dual-wavelength spectra obtained make this system an ideal pump source for difference frequency generation-based THz generation schemes.
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| 7. |
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| 8. |
- Duan, Zheng, et al.
(författare)
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Aquatic environment monitoring using a drone-based fluorosensor
- 2019
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Ingår i: Applied Physics B: Lasers and Optics. - : Springer Science and Business Media LLC. - 0946-2171. ; 125
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Tidskriftsartikel (refereegranskat)abstract
- A drone-based system for monitoring of laser-induced fluorescence from the aquatic environment was constructed. Fixed-range remote-sensing demonstration measurements were performed, and field recordings of natural river water fluorescence, oil-slicks as well as dye-marked natural water volumes were taken at drone flying heights of about 10 m. Our fluorosensor, weighing only 1.5 kg, and carried by a commercial drone, illustrates how airborne remote sensing based on fluorescence can be made cost-effective and readily applicable, while presently only in ambient low-light-level conditions.
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| 9. |
- Fomin, Alexey, et al.
(författare)
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Fiber Laser Intracavity Spectroscopy of hot water for temperature and concentration measurements
- 2015
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 121:3, s. 345-351
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of temperature and concentration measurements using near-IR (similar to 1.5 mu m) water spectra obtained by fiber laser intracavity spectroscopy was evaluated. The spectra were registered with water vapor heated in a tubular oven at temperatures between 1000 and 1300 K and in adiabatic flames where temperatures were above 1800 K. Adiabatic flames of methane were stabilized on the heat flux burner. For temperature and concentration evaluation, the observed spectra were fitted by simulated spectra calculated utilizing the HITEMP database. Several discrepancies between HITEMP data and the experiments leading to significant errors in evaluation were found. After small corrections to the database better, accuracy of the temperature (+/- 70 K) and concentration (+/- 20 %) measurements is obtained. A more precise spectroscopic assignment is needed to improve the accuracy of the results.
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| 10. |
- Ghorbani, Ramin, et al.
(författare)
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Real-time breath gas analysis of CO and CO2 using an EC-QCL
- 2017
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Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer. - 0946-2171 .- 1432-0649. ; 123:5
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Tidskriftsartikel (refereegranskat)abstract
- Real-time breath gas analysis is a promising, non-invasive tool in medical diagnostics, and well-suited to investigate the physiology of carbon monoxide (CO), a potential biomarker for oxidative stress and respiratory diseases. A sensor for precise, breath-cycle resolved, simultaneous detection of exhaled CO (eCO) and carbon dioxide (eCO2) was developed based on a continuous wave, external-cavity quantum cascade laser (EC-QCL), a low-volume multi-pass cell and wavelength modulation spectroscopy. The system achieves a noise-equivalent (1σ) sensitivity of 8.5 × 10−8 cm−1 Hz−1/2 and (2σ) detection limits of 9 ± 2 ppbv and 650 ± 7 ppmv at 0.14 s spectrum acquisition time for CO and CO2, respectively. Integration over 15 s yields a precision of 0.6 ppbv for CO. The fact that the eCO2 expirograms measured by capnography and laser spectroscopy have essentially identical shape confirms true real-time detection. It is found that the individual eCO exhalation profiles from healthy non-smokers have a slightly different shape than the eCO2 profiles and exhibit a clear dependence on exhalation flow rate and breath-holding time. Detection of indoor air CO and broadband breath profiling across the 93 cm−1 mode-hop-free tuning range of the EC-QCL are also demonstrated.
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