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
Polycrystalline of[(Na_(0.535)K_(0.480))_(0.966)Li_(0.058)](Nb_(0.90)Ta_(0.10))O_(3)samples were prepared using the high-temperature solid-state reaction technique.X-ray diffraction(XRD)analysis indicates the formatio...Polycrystalline of[(Na_(0.535)K_(0.480))_(0.966)Li_(0.058)](Nb_(0.90)Ta_(0.10))O_(3)samples were prepared using the high-temperature solid-state reaction technique.X-ray diffraction(XRD)analysis indicates the formation of a single-phase with orthorhombic structure.AC impedance plots were used as tool to analyze the electrical behavior of the sample as a function of frequency at different temperatures.The AC impedance studies revealed the presence of grain effect,from 425℃onwards.Complex impedance analysis indicated non-Debye type dielectric relaxation.The Nyquist plot showed the negative temperature coefficient of resistance(NTCR)characteristic of NKLNT.The AC conductivity results were used to correlate with the barrier hopping(CBH)model to evaluate the binding energy(W_(m)),the minimum hopping distance(R_(min)),the density of states at Fermi level(N(E_(f))),and the activation energy of the compound.展开更多
(Bi_(0.5)Na_(0.5))_(0.94)Ba_(0.06)TiO_(3)+x%Ce_(2)O_(3)+y%La_(2)O_(3)+z%Y_(2)O_(3) compounds(named BNT-BT-x/y/z)were synthesized by a sol-gel technique,for (x,y,z)=(0,0,0),(0.25,0.25,0.25),(0.25,0.5,0.5),(0.5,0.25,0.2...(Bi_(0.5)Na_(0.5))_(0.94)Ba_(0.06)TiO_(3)+x%Ce_(2)O_(3)+y%La_(2)O_(3)+z%Y_(2)O_(3) compounds(named BNT-BT-x/y/z)were synthesized by a sol-gel technique,for (x,y,z)=(0,0,0),(0.25,0.25,0.25),(0.25,0.5,0.5),(0.5,0.25,0.25)and(0.5,0.5,0.25).The structural variation according to the different system compositions is investigated by X-ray diffraction analyses.The results shows that the addition of Ce_(2)O_(3),La_(2)O_(3) or Y_(2)O_(3) in BNT-BT system,do not modify the crystalline structure,and a rhombohedral-tetragonal morphotropic phase boundary is maintained for different dopant addition.The BNT-BT-x/y/z-based ceramics sintered at relatively low temperature(1100℃)exhibit a good densification ratio.The optimum dielectric and piezoelectric properties are obtained with the BNT-BT-0.5/0.25/0.25 composition.High dielectric properties at room temperature(ε_(r)>1000)and low dielectric losses(tanδ<4×10^(-2))are obtained for this composition.This compound exhibits a piezoelectric constant d_(33) of 95 pC/N,a good polarization behavior is observed with high remanent polarization P_(r) of 9.21μC/cm^(2) and low value coercitivefield E_(c) of 2.66 kV/mm.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Polycrystalline of[(Na_(0.535)K_(0.480))_(0.966)Li_(0.058)](Nb_(0.90)Ta_(0.10))O_(3)samples were prepared using the high-temperature solid-state reaction technique.X-ray diffraction(XRD)analysis indicates the formation of a single-phase with orthorhombic structure.AC impedance plots were used as tool to analyze the electrical behavior of the sample as a function of frequency at different temperatures.The AC impedance studies revealed the presence of grain effect,from 425℃onwards.Complex impedance analysis indicated non-Debye type dielectric relaxation.The Nyquist plot showed the negative temperature coefficient of resistance(NTCR)characteristic of NKLNT.The AC conductivity results were used to correlate with the barrier hopping(CBH)model to evaluate the binding energy(W_(m)),the minimum hopping distance(R_(min)),the density of states at Fermi level(N(E_(f))),and the activation energy of the compound.
文摘(Bi_(0.5)Na_(0.5))_(0.94)Ba_(0.06)TiO_(3)+x%Ce_(2)O_(3)+y%La_(2)O_(3)+z%Y_(2)O_(3) compounds(named BNT-BT-x/y/z)were synthesized by a sol-gel technique,for (x,y,z)=(0,0,0),(0.25,0.25,0.25),(0.25,0.5,0.5),(0.5,0.25,0.25)and(0.5,0.5,0.25).The structural variation according to the different system compositions is investigated by X-ray diffraction analyses.The results shows that the addition of Ce_(2)O_(3),La_(2)O_(3) or Y_(2)O_(3) in BNT-BT system,do not modify the crystalline structure,and a rhombohedral-tetragonal morphotropic phase boundary is maintained for different dopant addition.The BNT-BT-x/y/z-based ceramics sintered at relatively low temperature(1100℃)exhibit a good densification ratio.The optimum dielectric and piezoelectric properties are obtained with the BNT-BT-0.5/0.25/0.25 composition.High dielectric properties at room temperature(ε_(r)>1000)and low dielectric losses(tanδ<4×10^(-2))are obtained for this composition.This compound exhibits a piezoelectric constant d_(33) of 95 pC/N,a good polarization behavior is observed with high remanent polarization P_(r) of 9.21μC/cm^(2) and low value coercitivefield E_(c) of 2.66 kV/mm.
