The generation of a plasma with an ultrahigh energy density of 1.2 GJ/cm^(3)(which corresponds to about 12 Gbar pressure) is investigated by irradiating thin stainless-steel foils with high-contrast femtosecond laser ...The generation of a plasma with an ultrahigh energy density of 1.2 GJ/cm^(3)(which corresponds to about 12 Gbar pressure) is investigated by irradiating thin stainless-steel foils with high-contrast femtosecond laser pulses with relativistic intensities of up to 10^(22) W/cm^(2).The plasma parameters are determined by X-ray spectroscopy.The results show that most of the laser energy is absorbed by the plasma at solid density,indicating that no pre-plasma is generated in the current experimental setup.展开更多
Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target i...Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~10^(22)W/cm^(2)laser±plasma experiment.We used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel targets.We discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy(i.e.,around half of the short Rayleigh length)and show that several diagnostics(in particular,3ωreflection and on-axis hard X-rays)can ensure this accuracy.We demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity on-target.Our approach is relatively fast(it requires 10±20 laser shots)and does not rely on the coincidence of low-power and high-power focal planes.展开更多
Laser wakefield acceleration,as an advanced accelerator concept,has attracted great attentions for its ultrahigh acceleration gradient and the capability to produce high brightness electron bunches.The three-dimension...Laser wakefield acceleration,as an advanced accelerator concept,has attracted great attentions for its ultrahigh acceleration gradient and the capability to produce high brightness electron bunches.The three-dimensional(3D)density serves as an evaluation metric for the particle bunch quality and is intrinsically related to the applications of an accelerator.Despite its significance,this parameter has not been experimentally measured in the investigation of laser wakefield acceleration.We report on an electro-optic 3D snapshot of a laser wakefield electron bunch at a position outside the plasma.The 3D shape of the electron bunch was detected by simultaneously performing optical transition radiation imaging and electro-optic sampling.Detailed 3D structures to a few micrometer levels were reconstructed using a genetic algorithm.The electron bunch possessed a transverse size of less than 30 micrometers.The current profile shows a multi-peak structure.The main peak had a duration of<10 fs and a peak current>1 kA.The maximum electron 3D number density was~9×10^(21)m^(-3).This research demonstrates a feasible way of 3D density monitoring on femtosecond kilo-ampere electron bunches,at any position of a beam transport line for relevant applications.展开更多
Supersonic gas jets generated via a conical nozzle are widely applied in the laser wakefield acceleration of electrons.The stability of the gas jet is critical to the electron injection and the reproducibility of the ...Supersonic gas jets generated via a conical nozzle are widely applied in the laser wakefield acceleration of electrons.The stability of the gas jet is critical to the electron injection and the reproducibility of the wakefield acceleration.Here we discussed the role of the stilling chamber in a modified converging-diverging nozzle to dissipate the turbulence and to stabilize the gas jets.By the fluid dynamics simulations and the Mach-Zehnder interferometer measurements,the instability originating from the nonlinear turbulence is studied and the mechanism to suppress the instability is proposed.Both the numerical and experimental results prove that the carefully designed nozzle with a stilling chamber is able to reduce the perturbation by more than 10% compared with a simple-conical nozzle.展开更多
基金carried out within the framework of Program 10 “Experimental laboratory astrophysics and geophysics,NCPM.”。
文摘The generation of a plasma with an ultrahigh energy density of 1.2 GJ/cm^(3)(which corresponds to about 12 Gbar pressure) is investigated by irradiating thin stainless-steel foils with high-contrast femtosecond laser pulses with relativistic intensities of up to 10^(22) W/cm^(2).The plasma parameters are determined by X-ray spectroscopy.The results show that most of the laser energy is absorbed by the plasma at solid density,indicating that no pre-plasma is generated in the current experimental setup.
基金financial support from ELI-Beamlinesproject Advanced Research using High Intensity Laser Produced Photons and Particles(ADONIS)(Project No.CZ.02.1.01/0.0/0.0/16_019/0000789)from the European Regional Development Fund+5 种基金QST-IRIthe QST President’s Strategic Grant(Creative Research)JSPS KAKENHI JP17F17811,JP19KK0355,JP19H00669 and JP22H01239the Czech Ministry of EducationYouth and Sports(CMEYS)for the financial support of the project number LM2023068partly supported by JSPS KAKENHI Grant No.JP23H01151。
文摘Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~10^(22)W/cm^(2)laser±plasma experiment.We used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel targets.We discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy(i.e.,around half of the short Rayleigh length)and show that several diagnostics(in particular,3ωreflection and on-axis hard X-rays)can ensure this accuracy.We demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity on-target.Our approach is relatively fast(it requires 10±20 laser shots)and does not rely on the coincidence of low-power and high-power focal planes.
基金Dr.I.Daito,Dr.T.P.Otsuka,and Dr.Y.Sakai.This work was funded by the JST-Mirai Program Grant No.JPMJMI17A1,Japan,JSPS KAKENHI(No.JP21K17998,No.JP23K17152,No.JP22K12665),Japan and the QST President's Strategic Grant(Exploratory Research),Japan.
文摘Laser wakefield acceleration,as an advanced accelerator concept,has attracted great attentions for its ultrahigh acceleration gradient and the capability to produce high brightness electron bunches.The three-dimensional(3D)density serves as an evaluation metric for the particle bunch quality and is intrinsically related to the applications of an accelerator.Despite its significance,this parameter has not been experimentally measured in the investigation of laser wakefield acceleration.We report on an electro-optic 3D snapshot of a laser wakefield electron bunch at a position outside the plasma.The 3D shape of the electron bunch was detected by simultaneously performing optical transition radiation imaging and electro-optic sampling.Detailed 3D structures to a few micrometer levels were reconstructed using a genetic algorithm.The electron bunch possessed a transverse size of less than 30 micrometers.The current profile shows a multi-peak structure.The main peak had a duration of<10 fs and a peak current>1 kA.The maximum electron 3D number density was~9×10^(21)m^(-3).This research demonstrates a feasible way of 3D density monitoring on femtosecond kilo-ampere electron bunches,at any position of a beam transport line for relevant applications.
基金funded by the JST-MIRAI program,grant No.JPMJMI17A1.
文摘Supersonic gas jets generated via a conical nozzle are widely applied in the laser wakefield acceleration of electrons.The stability of the gas jet is critical to the electron injection and the reproducibility of the wakefield acceleration.Here we discussed the role of the stilling chamber in a modified converging-diverging nozzle to dissipate the turbulence and to stabilize the gas jets.By the fluid dynamics simulations and the Mach-Zehnder interferometer measurements,the instability originating from the nonlinear turbulence is studied and the mechanism to suppress the instability is proposed.Both the numerical and experimental results prove that the carefully designed nozzle with a stilling chamber is able to reduce the perturbation by more than 10% compared with a simple-conical nozzle.
