Laser-driven neutron sources could offer a promising alternative to those based on conventional accelerator technologies in delivering compact beams of high brightness and short duration.We examine this through partic...Laser-driven neutron sources could offer a promising alternative to those based on conventional accelerator technologies in delivering compact beams of high brightness and short duration.We examine this through particle-in-cell and Monte Carlo simulations that model,respectively,the laser acceleration of protons from thin-foil targets and their subsequent conversion into neutrons in secondary lead targets.Laser parameters relevant to the 0.5 PW LMJ-PETAL and 0.6–6 PW Apollon systems are considered.Owing to its high intensity,the 20-fs-duration 0.6 PW Apollon laser is expected to accelerate protons up to above 100MeV,thereby unlocking efficient neutron generation via spallation reactions.As a result,despite a 30-fold lower pulse energy than the LMJ-PETAL laser,the 0.6 PW Apollon laser should perform comparably well both in terms of neutron yield and flux.Notably,we predict that very compact neutron pulses,of∼10 ps duration and∼100μm spot size,can be released provided the lead convertor target is thin enough(∼100μm).These sources are characterized by extreme fluxes,of the order of 10^(23) n cm^(−2) s^(−1),and even ten times higher when using the 6 PW Apollon laser.Such values surpass those currently achievable at large-scale accelerator-based neutron sources(∼10^(16) n cm^(−2) s^(−1)),or reported from previous laser experiments using low-Z converters(∼10^(18) n cm^(−2) s^(−1)).By showing that such laser systems can produce neutron pulses significantly brighter than existing sources,our findings open a path toward attractive novel applications,such as flash neutron radiography and laboratory studies of heavy-ion nucleosynthesis.展开更多
It was in 1995 that, at the end of the international project IEEY （International Equatorial Electrojet Year）, African and European scientists decided to create the IRGGEA （International Group in Geophysics Europe A...It was in 1995 that, at the end of the international project IEEY （International Equatorial Electrojet Year）, African and European scientists decided to create the IRGGEA （International Group in Geophysics Europe Africa） in order to pursue the scientific work started during the IEEY project, The main objective of IRGGEA was to introduce new fields of research in Africa and built teams of African scientists recognized at an international level in these new fields. To reach this goal, we developed days after days methods to manage smoothly a large network of scientists from developed and developing countries. After a short introduction on the field of research developed in the IRGGEA, we present the organization of the work based on sharing practices and the results obtained in terms of scientific publications and socio-cultural aspects as the increase of the number of women and positions for students in their countries. Such an experience is easy to reproduce.展开更多
In this paper,the effects of an electron beam on X-pinch-produced spectra of L-shellMoplasma are investigated for the first time by principal component analysis(PCA);this analysis is compared with that of line ratio d...In this paper,the effects of an electron beam on X-pinch-produced spectra of L-shellMoplasma are investigated for the first time by principal component analysis(PCA);this analysis is compared with that of line ratio diagnostics.A spectral database for PCA extraction is arranged using a non-Local Thermodynamic Equilibrium(non-LTE)collisional radiative L-shell Mo model.PC vector spectra of L-shell Mo,including F,Ne,Na and Mg-like transitions are studied to investigate the polarization types of these transitions.PC1 vector spectra of F,Ne,Na and Mg-like transitions result in linear polarization of Stokes Q profiles.Besides,PC2 vector spectra show linear polarization of Stokes U profiles of 2p^(5)3s of Ne-like transitions which are known as responsive to a magnetic field[Trabert,Beiersdorfer,and Crespo Lo´pez-Urrutia,Nucl.InstrumMethods Phys.Res.,Sect.B 408,107–109(2017)].A 3D representation of PCA coefficients demonstrates that addition of an electron beam to the non-LTE model generates quantized,collective clusters which are translations of each other that follow V-shaped cascade trajectories,except for the case f=0.0.The extracted principal coefficients are used as a database for an Artificial Neural Network(ANN)to estimate the plasma electron temperature,density and beam fractions of the time-integrated,spatially resolved L-shellMoX-pinch plasma spectrum.PCA-based ANNs provide an advantage in reducing the network topology,with a more efficient backpropagation supervised learning algorithm.The modeled plasma electron temperature is about Te;660 eV and density n_(e)=1×10^(20) cm^(-3),in the presence of the fraction of the beams with f-0.1 and centered energy of 5 keV.展开更多
This paper brings the comparison of performances of CO_(2)conversion by plasma and plasma-assisted catalysis based on the data collected from literature in this field,organised in an open access online database.This t...This paper brings the comparison of performances of CO_(2)conversion by plasma and plasma-assisted catalysis based on the data collected from literature in this field,organised in an open access online database.This tool is open to all users to carry out their own analyses,but also to contributors who wish to add their data to the database in order to improve the relevance of the comparisons made,and ultimately to improve the efficiency of CO_(2)conversion by plasma-catalysis.The creation of this database and database user interface is motivated by the fact that plasma-catalysis is a fast-growing field for all CO_(2)conversion processes,be it methanation,dry reforming of methane,methanolisation,or others.As a result of this rapid increase,there is a need for a set of standard procedures to rigorously compare performances of different systems.However,this is currently not possible because the fundamental mechanisms of plasma-catalysis are still too poorly understood to define these standard procedures.Fortunately however,the accumulated data within the CO_(2)plasma-catalysis community has become large enough to warrant so-called“big data”studies more familiar in the fields of medicine and the social sciences.To enable comparisons between multiple data sets and make future research more effective,this work proposes the first database on CO_(2)conversion performances by plasma-catalysis open to the whole community.This database has been initiated in the framework of a H_(2)0_(2)0 European project and is called the“PIONEER Data Base”.The database gathers a large amount of CO_(2)conversion performance data such as conversion rate,energy efficiency,and selectivity for numerous plasma sources coupled with or without a catalyst.Each data set is associated with metadata describing the gas mixture,the plasma source,the nature of the catalyst,and the form of coupling with the plasma.Beyond the database itself,a data extraction tool with direct visualisation features or advanced filtering functionalities has been developed and is available online to the public.The simple and fast visualisation of the state of the art puts new results into context,identifies literal gaps in data,and consequently points towards promising research routes.More advanced data extraction illustrates the impact that the database can have in the understanding of plasma-catalyst coupling.Lessons learned from the review of a large amount of literature during the setup of the database lead to best practice advice to increase comparability between future CO_(2)plasma-catalytic studies.Finally,the community is strongly encouraged to contribute to the database not only to increase the visibility of their data but also the relevance of the comparisons allowed by this tool.展开更多
A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-d...A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-dimensional cusp boundary from a two-dimensional X-ray image because the detected X-ray signals will be integrated along the line of sight.In this work,a global magnetohydrodynamic code was used to simulate the X-ray images and photon count images,assuming an interplanetary magnetic field with a pure Bz component.The assumption of an elliptic cusp boundary at a given altitude was used to trace the equatorward and poleward boundaries of the cusp from a simulated X-ray image.The average discrepancy was less than 0.1 RE.To reduce the influence of instrument effects and cosmic X-ray backgrounds,image denoising was considered before applying the method above to SXI photon count images.The cusp boundaries were reasonably reconstructed from the noisy X-ray image.展开更多
基金This work was supported by the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant Agreement No.787539)It was also supported by Grant No.ANR-17-CE30-0026-Pinnacle from the Agence Nationale de la Recherche+6 种基金We acknowledge GENCI,France,for granting us access to HPC resources at TGCC/CCRT(Allocation No.A0010506129)S.N.C.acknowledges support from the Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase II,a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund-the Competitiveness Operational Programme(1/07 July 2016,COP,ID 1334)by the project ELI-RO-2020-23 funded by IFA(Romania)The PETAL laser was designed and constructed by CEA under the financial auspices of the Conseil Régional d’Aquitaine,the French Ministry of Research,and the European UnionThe CRACC diagnostic was designed and commissioned on the LMJ-PETAL facility as a result of the PETAL+project coordinated by University of Bordeaux and funded by the French Agence Nationale de la Recherche under Grant No.ANR-10-EQPX-42-01The LMJ-PETAL experiment presented in this article was supported by the Association Lasers et Plasmas and by CEAThe diagnostics used in the experiment have been realized in the framework of the EquipEx PETAL+via Contract No.ANR-10-EQPX-0048.
文摘Laser-driven neutron sources could offer a promising alternative to those based on conventional accelerator technologies in delivering compact beams of high brightness and short duration.We examine this through particle-in-cell and Monte Carlo simulations that model,respectively,the laser acceleration of protons from thin-foil targets and their subsequent conversion into neutrons in secondary lead targets.Laser parameters relevant to the 0.5 PW LMJ-PETAL and 0.6–6 PW Apollon systems are considered.Owing to its high intensity,the 20-fs-duration 0.6 PW Apollon laser is expected to accelerate protons up to above 100MeV,thereby unlocking efficient neutron generation via spallation reactions.As a result,despite a 30-fold lower pulse energy than the LMJ-PETAL laser,the 0.6 PW Apollon laser should perform comparably well both in terms of neutron yield and flux.Notably,we predict that very compact neutron pulses,of∼10 ps duration and∼100μm spot size,can be released provided the lead convertor target is thin enough(∼100μm).These sources are characterized by extreme fluxes,of the order of 10^(23) n cm^(−2) s^(−1),and even ten times higher when using the 6 PW Apollon laser.Such values surpass those currently achievable at large-scale accelerator-based neutron sources(∼10^(16) n cm^(−2) s^(−1)),or reported from previous laser experiments using low-Z converters(∼10^(18) n cm^(−2) s^(−1)).By showing that such laser systems can produce neutron pulses significantly brighter than existing sources,our findings open a path toward attractive novel applications,such as flash neutron radiography and laboratory studies of heavy-ion nucleosynthesis.
文摘It was in 1995 that, at the end of the international project IEEY （International Equatorial Electrojet Year）, African and European scientists decided to create the IRGGEA （International Group in Geophysics Europe Africa） in order to pursue the scientific work started during the IEEY project, The main objective of IRGGEA was to introduce new fields of research in Africa and built teams of African scientists recognized at an international level in these new fields. To reach this goal, we developed days after days methods to manage smoothly a large network of scientists from developed and developing countries. After a short introduction on the field of research developed in the IRGGEA, we present the organization of the work based on sharing practices and the results obtained in terms of scientific publications and socio-cultural aspects as the increase of the number of women and positions for students in their countries. Such an experience is easy to reproduce.
文摘In this paper,the effects of an electron beam on X-pinch-produced spectra of L-shellMoplasma are investigated for the first time by principal component analysis(PCA);this analysis is compared with that of line ratio diagnostics.A spectral database for PCA extraction is arranged using a non-Local Thermodynamic Equilibrium(non-LTE)collisional radiative L-shell Mo model.PC vector spectra of L-shell Mo,including F,Ne,Na and Mg-like transitions are studied to investigate the polarization types of these transitions.PC1 vector spectra of F,Ne,Na and Mg-like transitions result in linear polarization of Stokes Q profiles.Besides,PC2 vector spectra show linear polarization of Stokes U profiles of 2p^(5)3s of Ne-like transitions which are known as responsive to a magnetic field[Trabert,Beiersdorfer,and Crespo Lo´pez-Urrutia,Nucl.InstrumMethods Phys.Res.,Sect.B 408,107–109(2017)].A 3D representation of PCA coefficients demonstrates that addition of an electron beam to the non-LTE model generates quantized,collective clusters which are translations of each other that follow V-shaped cascade trajectories,except for the case f=0.0.The extracted principal coefficients are used as a database for an Artificial Neural Network(ANN)to estimate the plasma electron temperature,density and beam fractions of the time-integrated,spatially resolved L-shellMoX-pinch plasma spectrum.PCA-based ANNs provide an advantage in reducing the network topology,with a more efficient backpropagation supervised learning algorithm.The modeled plasma electron temperature is about Te;660 eV and density n_(e)=1×10^(20) cm^(-3),in the presence of the fraction of the beams with f-0.1 and centered energy of 5 keV.
基金funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No.813393partially funded by the Portuguese FCT-Funda??o para a Ciência e a Tecnologia,under projects UIDB/50010/2020,UIDP/50010/2020 and PTDC/FIS-PLA/1616/2021。
文摘This paper brings the comparison of performances of CO_(2)conversion by plasma and plasma-assisted catalysis based on the data collected from literature in this field,organised in an open access online database.This tool is open to all users to carry out their own analyses,but also to contributors who wish to add their data to the database in order to improve the relevance of the comparisons made,and ultimately to improve the efficiency of CO_(2)conversion by plasma-catalysis.The creation of this database and database user interface is motivated by the fact that plasma-catalysis is a fast-growing field for all CO_(2)conversion processes,be it methanation,dry reforming of methane,methanolisation,or others.As a result of this rapid increase,there is a need for a set of standard procedures to rigorously compare performances of different systems.However,this is currently not possible because the fundamental mechanisms of plasma-catalysis are still too poorly understood to define these standard procedures.Fortunately however,the accumulated data within the CO_(2)plasma-catalysis community has become large enough to warrant so-called“big data”studies more familiar in the fields of medicine and the social sciences.To enable comparisons between multiple data sets and make future research more effective,this work proposes the first database on CO_(2)conversion performances by plasma-catalysis open to the whole community.This database has been initiated in the framework of a H_(2)0_(2)0 European project and is called the“PIONEER Data Base”.The database gathers a large amount of CO_(2)conversion performance data such as conversion rate,energy efficiency,and selectivity for numerous plasma sources coupled with or without a catalyst.Each data set is associated with metadata describing the gas mixture,the plasma source,the nature of the catalyst,and the form of coupling with the plasma.Beyond the database itself,a data extraction tool with direct visualisation features or advanced filtering functionalities has been developed and is available online to the public.The simple and fast visualisation of the state of the art puts new results into context,identifies literal gaps in data,and consequently points towards promising research routes.More advanced data extraction illustrates the impact that the database can have in the understanding of plasma-catalyst coupling.Lessons learned from the review of a large amount of literature during the setup of the database lead to best practice advice to increase comparability between future CO_(2)plasma-catalytic studies.Finally,the community is strongly encouraged to contribute to the database not only to increase the visibility of their data but also the relevance of the comparisons allowed by this tool.
基金funded by the National Natural Science Foundation of China(NNSFC)under Grant Numbers 42322408,42188101,and 42441809Additional support was provided by the Climbing Program of the National Space Science Center(NSSC,Grant No.E4PD3005)as well as the Specialized Research Fund for State Key Laboratories of China.
文摘A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-dimensional cusp boundary from a two-dimensional X-ray image because the detected X-ray signals will be integrated along the line of sight.In this work,a global magnetohydrodynamic code was used to simulate the X-ray images and photon count images,assuming an interplanetary magnetic field with a pure Bz component.The assumption of an elliptic cusp boundary at a given altitude was used to trace the equatorward and poleward boundaries of the cusp from a simulated X-ray image.The average discrepancy was less than 0.1 RE.To reduce the influence of instrument effects and cosmic X-ray backgrounds,image denoising was considered before applying the method above to SXI photon count images.The cusp boundaries were reasonably reconstructed from the noisy X-ray image.
