| 1. |
- Issa, F., et al.
(författare)
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4H-SiC neutron sensors based on ion implanted 10B neutron converter layer
- 2015
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Ingår i: 2015 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479999187
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Konferensbidrag (refereegranskat)abstract
- In the framework of the I-SMART project the main aim is to develop an innovative complete radiation detection system based on silicon carbide technology in view to detect neutrons (thermal and fast) and photons for harsh environments. In the present work two geometries have been realized based on ion implantation of boron. In the first geometry, 10B ions have been implanted into the Al metallic contact of a p-n diode to create the neutron converter layer. In the second geometry one single process has been used to realize both the p+-layer and the neutron converter layer. The technological processes followed to fabricate these detectors, with a study of their electrical behavior and their responses under thermal neutron irradiations are addressed in this paper.
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| 2. |
- Issa, F., et al.
(författare)
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Improvements in Realizing 4H-SiC Thermal Neutron Detectors
- 2016
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Ingår i: ISRD 15 - INTERNATIONAL SYMPOSIUM ON REACTOR DOSIMETRY. - : EDP Sciences. - 9782759819294
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Konferensbidrag (refereegranskat)abstract
- In this work we presented two types of 4H-SiC semiconductor detectors (D1 and D2) both based on ion implantation of B-10 inside the aluminum metallic contact. The first detector shows a high leakage current after the implantation and low signal to noise ratio. However, improvements concerning the implantation parameters and the distance between the implanted B-10 thermal neutron converter layer and the active pn-junction have led to low leakage current and thus to higher signal to noise ratio. This proves the strength of this new method of realizing sensitive SiC-based thermal neutron detectors.
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| 3. |
- Issa, F., et al.
(författare)
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Nuclear radiation detectors based on 4H-SiC p+-n junction
- 2014
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Ingår i: 15th International Conference on Silicon Carbide and Related Materials, ICSCRM 2013. - 9783038350101 ; , s. 1046-1049
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Konferensbidrag (refereegranskat)abstract
- Silicon carbide (SiC) radiation detectors were realized by 10B implantation into the metal contact in order to avoid implantation-related defects within the sensitive area of the 4H-SiC pn junction. No post implantation annealing was performed. Such detectors respond to thermal neutrons showing consistent counting rates as function of external reverse bias voltages and radiation intensity.
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| 4. |
- Issa, F., et al.
(författare)
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Radiation silicon carbide detectors based on ion implantation of boron
- 2014
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 61:4, s. 2105-2111
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Tidskriftsartikel (refereegranskat)abstract
- Radiation detectors based on radiation-hardened semiconductor such as silicon carbide (SiC), have received considerable attention in many applications such as in outer space, high energy physics experiments, gas and oil prospection, and nuclear reactors. In the frame work of the European project I-SMART (Innovative Sensor for Material Ageing and Radiation Testing), we demonstrated for the first time the reliability of thermal neutron detectors realized by standard ion implantation of boron atoms to form a neutron converter layer (NCL). Two types of detectors were realized; the first was implanted by aluminum to create the p+ - layer, and then implanted by boron ( 10 B) to realize the NCL. The second type was based on p+ - layer, and was implanted by 10B into the aluminum metallic contact in order to avoid implantation-related defect within the sensitive area. Both kinds of detectors reveal to respond to thermal neutrons and gamma rays, showing consistent counting rates as a function of bias voltages, radiation intensity and type of shielding.
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| 5. |
- Issa, F., et al.
(författare)
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Radiation silicon carbide detectors based on ion implantation of boron
- 2013
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Ingår i: 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013. - : IEEE. - 9781479910472 ; , s. 6727997-
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Konferensbidrag (refereegranskat)abstract
- Radiation detectors based on radiation-hardened semiconductor such as silicon carbide (SiC), have received considerable attention in many applications such as in outer space, high energy physics experiments, gas and oil prospection, and nuclear reactors. For the first time it was demonstrated the reliability of thermal neutron detectors realized by standard ion implantation of boron layer as a neutron converter layer. Moreover, these detectors respond to thermal neutrons and gamma rays showing different counting rates at different voltages and under different types of shielding.
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| 6. |
- Issa, F., et al.
(författare)
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Study of the stability of 4H-SiC detectors by thermal neutron irradiation
- 2015
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Ingår i: European Conference on Silicon Carbide and Related Materials, ECSCRM 2014. - : Trans Tech Publications Inc.. - 9783038354789 ; , s. 875-878
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Konferensbidrag (refereegranskat)abstract
- Two types of 4H-SiC semiconductor detectors (D1 and D2) are realized based on ion implantation of10B inside the aluminum metallic contact. The first detector shows a high leakage current after10B implantation and low signal to noise ratio. However, improvements concerning the implantation parameters led to lower leakage current and thus to higher signal to noise ratio. Moreover such detectors show their stability under different thermal neutron fluxes showing the reproducible features of the pulse height spectra and same electrical behaviour before and after irradiation. Some of future using and interesting applications of such SiC detector devices -for non-charged particles (photons and/or neutrons) are expected in the frame of non-destructive assays, nuclear reactor monitoring, safeguards, oil and gas prospection [1,2]
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| 7. |
- Pouransari, Zeinab, et al.
(författare)
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Analysis of combustion modeling tools using DNS of a non-premixed turbulent wall-jet
- 2012
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Ingår i: THMT-12. Proceedings of the Seventh International Symposium On Turbulence Heat and Mass Transfer. - : Begell House. ; , s. 115-120
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Konferensbidrag (refereegranskat)abstract
- Three-dimensional Direct Numerical Simulation (DNS) is used to study reaction in a non-premixed turbulent plane wall-jet. The flow is compressible and involves a reaction between an oxidizer and a fuel species The main objective of this study is to use DNS for validation and evaluation of different non-premixed combustion modeling tools. As the first step of this assessment, we have focused on RANS modeling aspects, distinguishing both the heat-release effects and the influences due to the presence of solid-walls. The present study adds to our previous knowledge on the behavior of models in different flow geometries.
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| 8. |
- Pouransari, Zeinab, et al.
(författare)
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DNS Analysis of Wall Heat Transfer and Combustion Regimes in a Turbulent Non-premixed Wall-jet Flame
- 2016
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Ingår i: Flow Turbulence and Combustion. - : Springer Netherlands. - 1386-6184 .- 1573-1987. ; , s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the heat-release effects on the wall heat transfer in turbulent reacting flows, i.e. heat transfer with or without significant density variation, is essential for a wide variety of industrial flows, especially combustion problems. The present study focuses on the wall heat transfer and the near-wall reaction characteristics. The heat-release effects on the wall heat transfer and skin-friction coefficients are investigated using three-dimensional direct numerical simulations of a turbulent reacting wall-jet flow with and without heat release. Reductions in the skin-friction coefficient are observed in the exothermic case, compared to the isothermal one, and the underlying mechanism is explained. The absolute wall heat flux also increases, while the corresponding Nusselt number decreases with increasing heat release. Furthermore, the wall effects on the near-wall average burning rate are assessed. It is found that the isothermal cold wall results in an appreciable decrease of the burning rate in the exothermic cases. We observed indications that the wall increases the chances for the development of the premixed mode and its occurrence is very fast in the wall-normal direction.
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| 9. |
- Pouransari, Zeinab, et al.
(författare)
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DNS analysis of wall heat transfer and combustion regimes in a turbulent nonpremixed wall-jet flame
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding the heat-release effects on the wall heat transfer in turbulent reacting flows, i.e. heat transfer with or without significant density variation, is essential for a wide variety of industrial flows, especially combustion problems. The present study focuses on the wall heat transfer and the near-wall reaction characteristics. The heat-release effects on the wall heat transfer and skin friction coefficients are investigated using three-dimensional direct numerical simulations of a turbulent reacting wall-jet flow with and without heat release. Reductions in the skin-friction coefficient are observed in the exothermic case, compared to the isothermal one, and the underlying mechanism is explained. The absolute wall heat flux also increases, while the corresponding Nusselt number decreases with increasing heat release. Furthermore, the wall effects on the near-wall average burning rate are assessed. It is found that the isothermal cold wall results in an appreciable decrease of the burning rate in the exothermic cases. We observed indications that the wall increases the chances for the development of the premixed mode and its occurrence is very fast in the wall normal direction.
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| 10. |
- Pouransari, Zeinab, et al.
(författare)
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Heat release effects on mixing scales of non-premixed turbulent wall-jets : A direct numerical simulation study
- 2013
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Ingår i: International Journal of Heat and Fluid Flow. - : Elsevier BV. - 0142-727X .- 1879-2278. ; 40, s. 65-80
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Tidskriftsartikel (refereegranskat)abstract
- The present study concerns the role of heat release effects on characteristics mixing scales of turbulence in reacting wall-jet flows. Direct numerical simulations of exothermic reacting turbulent wall-jets are performed and compared to the isothermal reacting case. An evaluation of the heat-release effects on the structure of turbulence is given by examining the mixture fraction surface characteristics, diagnosing vortices and exploring the dissipation rate of the fuel and passive scalar concentrations, and moreover by illustration of probability density functions of reacting species and scatter plots of the local temperature against the mixture fraction. Primarily, heat release effects delay the transition, enlarge the fluctuation intensities of density and pressure and also enhance the fluctuation level of the species concentrations. However, it has a damping effect on all velocity fluctuation intensities and the Reynolds shear stress. A key result is that the fine-scale structures of turbulence are damped, the surface wrinkling is diminished and the vortices become larger due to heat-release effects. Taking into account the varying density by using semi-local scaling improves the collapse of the turbulence statistics in the inner region, but does not eliminate heat release induced differences in the outer region. Examining the two-dimensional premultiplied spanwise spectra of the streamwise velocity fluctuations indicates a shifting in the positions of the outer peaks, associated with large energetic structures, toward the inner region.
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| 11. |
- Pouransari, Zeinab, et al.
(författare)
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Reynolds Number Effects on Statistics and Structure of an Isothermal Reacting Turbulent Wall-Jet
- 2014
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Ingår i: Flow Turbulence and Combustion. - : Springer Science and Business Media LLC. - 1386-6184 .- 1573-1987. ; 92:4, s. 931-945
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional direct numerical simulation (DNS) is used to investigate the effects of changing the Reynolds number on dynamics of a reacting turbulent wall-jet. The flow is compressible and a single-step isothermal global reaction is considered. At the inlet, fuel and oxidizer enter the domain separately in a non-premixed manner. In this study, the bulk Reynolds number of the flow, in terms of the inlet quantities, varies from Re = 2000 to Re = 6000, which results in a comparable change in friction Reynolds numbers. The DNS database in Pouransari et al. (Phys. Fluids 23(085104), 2011) is used for the lower Reynolds number case and for the higher Reynolds number case, a new DNS is performed. One of the main objectives of this study is to compare the influences of changing the Reynolds number of the isothermal flow with the heat-release effects caused by the chemical reaction, that we studied earlier in Pouransari et al. (Int. J. Heat Fluid Flows 40, 65-80, 2013). While, both turbulent and flame structures become finer at the higher Reynolds number, the effect of decreasing the Reynolds number and adding the combustion heat release are compared with each other and found to be similar for some aspects of the flow, but are not always the same.
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| 12. |
- Rasam, Amin, 1979-, et al.
(författare)
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An explicit algebraic subgrid-scale scalar variance model
- 2020
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Ingår i: ETC 2013 - 14th European Turbulence Conference. - : Zakon Group LLC.
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Konferensbidrag (refereegranskat)abstract
- We present a subgrid-scale (SGS) scalar variance model based on the explicit algebraic subgrid scalar flux model, EASSFM (8). The EASSFM is a dynamic mixed nonlinear tensor eddy diffusivity model, which is derived from the modeled transport equation of the SGS scalar flux. The explicit algebraic form is obtained using the weak equilibrium assumption. The resulting model improves the direction of the predicted SGS flux vector and enables the prediction of shear-induced SGS fluxes, in contrast with the eddy diffusivity model. The EASSFM has been used for large eddy simulation (LES) of turbulent channel flow with and without system rotation (8; 9) and has been found to improve LES predictions over the dynamic eddy diffusivity model. A priori analysis of the EASSFM using the filtered DNS data from a reacting turbulent wall-jet has been performed recently (6; 7), which also showed favorable results. In this study, we evaluate our SGS scalar variance model using the filtered DNS database of a turbulent reacting wall-jet, which is an extension of our previous study on reactive turbulent wall-jet flows (5; 7) to a larger simulation domain. The results show a good agreement between the filtered DNS and our model predictions for the passive and active scalars. This indicates that acceptable predictions of the SGS scalar variance can be obtained using the EASSFM with the new SGS scalar variance model.
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| 13. |
- Rasam, Amin, et al.
(författare)
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Assessment of subgrid-scale stress statistics in non-premixed turbulent wall-jet flames
- 2016
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Ingår i: Journal of Turbulence. - : Taylor & Francis. - 1468-5248. ; 17:5, s. 471-490
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the heat-release effects on the characteristics of the subgrid-scale (SGS) stress tensor and SGS dissipation of kinetic energy and enstrophy. Direct numerical simulation data of a non-premixed reacting turbulent wall-jet flow with and without substantial heat release is employed for the analysis. This study comprises, among others, an analysis of the eigenvalues of the resolved strain rate and SGS stress tensors, to identify the heat-release effects on their topology. An assessment of the alignment between the eigenvectors corresponding to the largest eigenvalues of these two tensors is also given to provide further information for modelling of the SGS stress tensor. To find out the heat-release effects on the dynamics of the turbulent kinetic energy and enstrophy dissipation, probability density functions (PDFs) and mean values are analysed. The mean SGS shear stress and turbulent kinetic energy both slightly increase in the buffer layer and substantially decrease further away from the wall, due to the heat-release effects. Contrary to the kinetic energy, heat release decreases the mean SGS dissipation of enstrophy in the near-wall region. Moreover, differences in the shapes of the PDFs between the isothermal and exothermic cases indicate changes in the intermittency level of both SGS dissipations. Heat release also increases the SGS stress anisotropy in the near-wall region. Although, the structure of the mean resolved strain-rate tensor only marginally differs between the isothermal and exothermic cases in the near-wall region, substantial differences are observed in the jet area, where compressibility effects are important and heat-release effects are found to promote compression states. The differences in the relative alignment between the SGS stress and resolved strain-rate tensors in the isothermal and exothermic cases are discussed in connection with the differences in the SGS dissipation of kinetic energy.
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| 14. |
- Rasam, Amin, et al.
(författare)
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Assessment of subgrid-scale stress statistics in non-premixed turbulent wall-jet flames
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We investigate the properties of the subgrid-scale (SGS) stress tensor and SGS dissipation of kinetic energy and enstrophy,using the direct numerical simulation (DNS) data of a non-premixed reacting turbulent wall-jet flow, with and without heat release.The separation of scales, to obtain the SGS quantities, is achieved by application of a box filter.This study comprises an analysis on the topology of the resolved strain-rate andSGS stress tensors, through an assessment of their eigenvectors and their relative alignment. To find out the heat-release effects on the dynamics of the turbulent energy dissipation, SGS dissipation of kinetic energy andenstrophy are evaluated using length-scale, probability density functions (PDFs) and mean value analysis.It is found that the mean SGS shear stress and turbulent kinetic energy are suppressed by the heat release, whilethe SGS anisotropy is substantially increased.Although, the topology of the resolved strain-rate tensor only marginally differs between the isothermal and exothermic cases in the near-wall wall region,substantial differences are observed in the shear layer in the jet area, where the compressibility effects are large andthe exothermic effects are found to promote compression states.The relative alignment between the SGS stress and resolved strain-rate tensors is also affected by the heat release.The mean SGS dissipation of kinetic energy is increased, while the SGS dissipation of enstrophy is decreased by the heat release.Interesting differences in the shape of the PDFs of the SGS dissipation are observed between the isothermal and exothermic cases, such as thechange in the intermittency of both SGS dissipation terms.
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| 15. |
- Vervisch, V., et al.
(författare)
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Nuclear radiation detector based on ion implanted p-n junction in 4H-SiC
- 2013
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Ingår i: 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013. - : IEEE. - 9781479910472 ; , s. 6728002-
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a new device detector based on ion implanted p-n junction in 4H-SiC for nuclear instrumentation. We showed the interest to use 10Boron as a Neutron Converter Layer in order to detect thermal neutrons. We present the main results obtained during irradiation tests performed in the Belgian Reactor 1. We show the capability of our detector by means of first results of the detector response at different reverse voltage biases and at different reactor power.
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