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Response Time of a Fiber Bragg Grating Based Hydrogen Sensor for Transformer Monitoring
摘要： We developed and optimized a new fiber optic sensor using palladium foils attached to optical fiber Bragg gratings (FBG) for hydrogen measurements. Fifteen in parallel processed sensors were characterized and qualified in two custom tailored experimental set ups and their response to a 5% hydrogen/nitrogen gas mixture and the same gas bubbled trough transformer oil was measured. The hydrogen response is similar for both medium and close to the theoretical maximum sensitivity, but the response time was found to be very different, much slower in oil than in gas. A theoretical comparison of hydrogen diffusion trough palladium and hydrogen absorption on the palladium surface as well as a measurement of the hydrogen uptake and diffusion trough the oil to the sensor have been done to investigate the origin of the different response time. They indicate that the response time determining step is the absorption of hydrogen on the palladium surface and that this process is slowed down in oil compared to a pure gas environment.
关键词： hydrogen sensor,fibre Bragg grating (FBG),fiber sensor,palladium based sensors,hydrogen diffusion and absorption in oil
更新于2025-09-23 15:22:29
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Calculations of adsorption energies, coadsorptions, and diffusion barriers of H atoms, and the H <sub/>2</sub> formation on a nanographene surface (coronene)
摘要： Adsorption and diffusion of ortho, meta, and para cis hydrogen dimers, on central and edge rings of coronene (nanographene), were studied by using the DFT-D method, considering different multiplicities. Calculated values of adsorption energy, coadsorption energy, diffusion barriers, and reaction barriers for the H2 formation (Langmuir-Hinshelwood (LH) mechanism) were evaluated for ortho and para locations. The adsorption of an H atom increases the adsorption energy of another hydrogen (coadsorption). The most stable dimers are those where an H is adsorbed on hydrogenated-edge sites. Dimers with multiplicity M = 1, with H separated by an odd number of bonds, have higher coadsorption energies (higher diffusion barriers) than those where the separation is by an even number. The H2 formation is more feasible on edge-edge and edge-center sites; however, on ortho hydrogenated-edge sites, it is not energetically favored. For M = 3, H2 formation is not observed because desorption of H occurs.
关键词： H2 formation,interstellar media catalysis,nanographene,coronene,hydrogen diffusion
更新于2025-09-23 15:22:29
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Tests under irradiation of optical fibers and cables devoted to corium monitoring in case of severe accident in a Nuclear Power Plant
摘要： The DISCOMS project, which stands for “DIstributed Sensing for COrium Monitoring and Safety”, considers the potential of distributed sensing technologies, based on remote instrumentations and Optical Fiber Sensing cables embedded into the concrete floor under the reactor vessel, to monitor the status of this third barrier of confinement. This paper focuses on the selection and testing of singlemode (SM) optical fibers with limited RIA (Radiation Induced Attenuation) to be compliant with remote distributed instruments optical budgets, the ionizing radiation doses to sustain, and their reduction provided by the concrete basemat shielding. The tests aimed at exposing these fibers and the corresponding sensitive optical cables, to the irradiation doses expected during the normal operation of the reactor (up to 60 years for the European Pressurized Reactor), followed by a severe accident. Several gamma and mixed (neutron-gamma) irradiations were performed at CEA Saclay facilities: POSé?DON irradiator and ISIS reactor, up to a gamma cumulated dose of about 2 MGy and fast neutron fluence (E > 1 MeV) of 6 x 1015 n/cm2. The first gamma test permitted to assess the RIA at various optical wavelengths, and to select three radiation tolerant singlemode fibers (RIA < 5 dB/100 m, at 1550 nm operating wavelength). The second one was performed on voluminous strands of sensitive cables encapsulating selected optical fibers, up to approximately the same accumulated dose, at two temperatures: 30°C and 80°C. A significant increase of the RIA, without any saturation tendency, appeared for fibers inserted into cables, correlated with the increase of the hydroxyl attenuation peak at 1380 nm. Molecular hydrogen generated by the radiolysis of compounds of the cable is at the origin of this phenomenon. A third gamma irradiation run permitted to measure the radiolytic hydrogen production yield of some compounds of a dedicated temperature cable sample. The efficiency of a carbon coating layer over the silica cladding, acting as a barrier against hydrogen diffusion, was also successfully confirmed. Finally, the efficiency of this carbon coating layer has also been tested under neutron irradiation, then qualified as a protection barrier against hydrogen diffusion in the optical fiber cores.
关键词： carbon coating layer,radiation effects,optical fibers,hydrogen diffusion,gamma,radiolysis,rad-hard optical fiber,neutron,distributed measurement
更新于2025-09-23 15:21:01
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Impact of laser treatment on hydrogenated amorphous silicon properties
摘要： The application of laser radiation to locally modify the hydrogen distribution within hydrogenated amorphous silicon films on a short time scale is studied. The impact of laser power and irradiation time on the temperature of the silicon layer during the laser treatment and the hydrogen outdiffusion is analyzed. Moreover, the resulting optoelectronic properties of the amorphous silicon are examined. On a timescale of a few seconds or less, we can successfully decrease the hydrogen concentration in the surface-near region of the silicon layer without major impact on the optoelectronic properties.
关键词： laser treatment,amorphous silicon,hydrogen diffusion
更新于2025-09-23 15:19:57
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P-1.6: Effect of Deposition Condition of Passivation Layer on the Performance of Self-Aligned Top-Gate a-IGZO TFTs
摘要： In this paper, we fabricated self-aligned top-gate (SATG) amorphous thin-film transistors (TFTs). The conductive source/drain regions were formed by hydrogen incorporation during the deposition of SiOx or SiNx passivation layer using plasma-enhanced chemical vapor deposition (PECVD). The effect of passivation layer deposition condition on the electrical performance of self-aligned top-gate a-IGZO TFTs was investigated. It was shown that the source-drain parasitic resistance (Rsd) was effectively reduced during the deposition of SiNx passivation layer than SiOx. However, as the deposition temperature of SiNx passivation layer increased, hydrogen lateral diffusion into channel region resulted in the shrinkage of effective channel length and the deterioration of electrical performance of short-channel device.
关键词： thin-film transistors,hydrogen diffusion,self-aligned top-gate,a-IGZO
更新于2025-09-19 17:15:36
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Hydrogen diffusion from PECVD silicon nitride into multicrystalline silicon wafers: Elastic recoil detection analysis (ERDA) measurements and impact on light and elevated temperature induced degradation (LeTID)
摘要： Hydrogen is a crucial element for crystalline silicon solar cells due to its ability to passivate bulk defects in silicon. The introduction and distribution of hydrogen has gained a lot of interest due to its proposed involvement in the phenomenon termed “light and elevated temperature induced degradation” (LeTID) in multicrystalline silicon (mc-Si) solar cells. LeTID, which can cause an efficiency loss of about 6-14% (relative) for mc-Si PERC (passivated emitter and rear cell) devices upon exposure to elevated temperature and illumination, is a serious cause of concern for the silicon photovoltaic industry. Interaction of hydrogen with mc-Si is complex as mc-Si contains grain boundaries, dislocations, large concentrations of impurities and traps which may affect the diffusivity of hydrogen in silicon. Understanding the diffusion of hydrogen in mc-Si, and how it affects LeTID, is therefore of great interest. In this contribution, the concentration of hydrogen diffused into p-type mc-Si lifetime samples from hydrogen-rich passivation layers (SiNx:H and AlOx:H) fired at different peak firing temperatures is measured by elastic recoil detection analysis (ERDA) along with Rutherford backscattering (RBS). Also, experiments are done to study the impact of annealing in the presence of hydrogen on the extent of LeTID. A correlation is established between the hydrogen concentration diffused into silicon bulk and the extent of LeTID in lifetime samples fired at different peak firing profiles.
关键词： light and elevated temperature induced degradation,multicrystalline silicon wafers,PECVD silicon nitride,elastic recoil detection analysis,Hydrogen diffusion
更新于2025-09-12 10:27:22
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Coherent Anti-Stokes Raman Spectroscopy of a Hydrogen Diffusion Flame in a Ramjet
摘要： Dual-pump coherent anti-Stokes Raman spectroscopy (CARS) was used to measure the mole fractions of major species as well as the rotational and vibrational temperatures of molecular nitrogen in a hydrogen-fueled dual-mode scramjet flowpath operated in the “ram” mode. Developments in CARS methods and uncertainties are described, including a detailed analysis of the effects of spatial averaging. The mean and standard deviation of the turbulent fluctuations of the temperature and mole fractions at multiple planes in the flowpath and scatter plots of vibrational and rotational temperature are presented. The flame is stabilized downstream of the ramp and grows under the influence of turbulence and rollup of the counterrotating vortex pair formed at the ramp; combustion continues in accelerating flow approaching the end of the measurement domain. Thermal nonequilibrium is observed in the mixing of air with the molecular hydrogen jet close to the injector. Spatial averaging errors are significant at some locations; new methods to correct these errors are described.
关键词： Coherent Anti-Stokes Raman Spectroscopy,CARS,thermal nonequilibrium,hydrogen diffusion flame,supersonic combustion,spatial averaging,ramjet
更新于2025-09-04 15:30:14