We present a systematic experimental investigation of temporal contrast enhancement techniques for petawatt(PW)-class Ti:sapphire lasers utilizing a double chirped-pulse amplification(CPA)architecture.Particular atten...We present a systematic experimental investigation of temporal contrast enhancement techniques for petawatt(PW)-class Ti:sapphire lasers utilizing a double chirped-pulse amplification(CPA)architecture.Particular attention is given to pre-pulses induced by post-pulses originating in the first CPA stage.One conventional and two advanced pulse-cleaning strategies are quantitatively evaluated:(i)a saturable absorber(SA),(ii)a femtosecond optical parametric amplifier(OPA)employing the idler pulse in a two-stage configuration,and(iii)sum-frequency generation(SFG)combining the signal and idler pulses from the OPA.All techniques are implemented and evaluated using the J-KAREN-P laser system with an output energy of about 20 J.To the best of our knowledge,this is the first report to directly and systematically compare the contrast of pre-pulses originating from the first CPA stage under identical experimental conditions in a high-energy PW-class laser facility.The results offer crucial insights into contrast optimization for future high-field applications.展开更多
Laser-driven ion sources are a rapidly developing technology producing high energy,high peak current beams.Their suitability for applications,such as compact medical accelerators,motivates development of robust accele...Laser-driven ion sources are a rapidly developing technology producing high energy,high peak current beams.Their suitability for applications,such as compact medical accelerators,motivates development of robust acceleration schemes using widely available repetitive ultraintense femtosecond lasers.These applications not only require high beam energy,but also place demanding requirements on the source stability and controllability.This can be seriously affected by the laser temporal contrast,precluding the replication of ion acceleration performance on independent laser systems with otherwise similar parameters.Here,we present the experimental generation of>60 MeV protons and>30 MeV u-1 carbon ions from sub-micrometre thickness Formvar foils irradiated with laser intensities>1021 Wcm2.Ions are accelerated by an extreme localised space charge field≥30TVm-1,over a million times higher than used in conventional accelerators.The field is formed by a rapid expulsion of electrons from the target bulk due to relativistically induced transparency,in which relativistic corrections to the refractive index enables laser transmission through normally opaque plasma.We replicate the mechanism on two different laser facilities and show that the optimum target thickness decreases with improved laser contrast due to reduced pre-expansion.Our demonstration that energetic ions can be accelerated by this mechanism at different contrast levels relaxes laser requirements and indicates interaction parameters for realising application-specific beam delivery.展开更多
We report on the design and characterization of the plasma mirror system installed on the J-KAREN-P laser at the Kansai Photon Science Institute,National Institutes for Quantum Science and Technology.The reflectivity ...We report on the design and characterization of the plasma mirror system installed on the J-KAREN-P laser at the Kansai Photon Science Institute,National Institutes for Quantum Science and Technology.The reflectivity of the single plasma mirror system exceeded 80%.In addition,the temporal contrast was improved by two orders of magnitude at 1 ps before the main pulse.Furthermore,the laser near-field spatial distribution after the plasma mirror was kept constant at plasma mirror fluence of less than 100 kJ/cm^(2).We also present the results of investigating the difference and the fluctuation in energy,pulse width and pointing stability with and without the plasma mirror system.展开更多
基金supported by the Japan Society for the Promotion of Science(Grant Nos.JP 15F15772,JP 16H03911,JP 16K05506,JP 19H00669,and JP 25H00621)the Precursory Research for Embryonic Science and Technology(Grant No.JPMJPR16P9)+1 种基金the MEXT Project(Grant No.JPMXS0450300221)the Japan Science and Technology Agency(Grant No.PRESTOJPMJPR16P9).
文摘We present a systematic experimental investigation of temporal contrast enhancement techniques for petawatt(PW)-class Ti:sapphire lasers utilizing a double chirped-pulse amplification(CPA)architecture.Particular attention is given to pre-pulses induced by post-pulses originating in the first CPA stage.One conventional and two advanced pulse-cleaning strategies are quantitatively evaluated:(i)a saturable absorber(SA),(ii)a femtosecond optical parametric amplifier(OPA)employing the idler pulse in a two-stage configuration,and(iii)sum-frequency generation(SFG)combining the signal and idler pulses from the OPA.All techniques are implemented and evaluated using the J-KAREN-P laser system with an output energy of about 20 J.To the best of our knowledge,this is the first report to directly and systematically compare the contrast of pre-pulses originating from the first CPA stage under identical experimental conditions in a high-energy PW-class laser facility.The results offer crucial insights into contrast optimization for future high-field applications.
基金supported by Kakenhi Grant No.16K05506,Grant No.20H00140,Grant No.21KK0049,Grant No.22H00121,JST PRESTO Grant No.JPMJPR16P9,QST President's Strategic Grant(QST) International Research Initiative(AAA98)and Creative Research(ABACS),and by Laserlab Europe V(PRISES,contract no.871124)supported by EU's Horizon 2020 research and innovation program under the Marie Sktodowska-Curie grant agreement No 894679support by JST-Mirai Program Grant Number JPMJMI17A1,Japan.N.P.D.,EJ.D.,G.S.H.,Z.N.acknowledge support from STFC grants ST/P002021/1,STN001639/1.
文摘Laser-driven ion sources are a rapidly developing technology producing high energy,high peak current beams.Their suitability for applications,such as compact medical accelerators,motivates development of robust acceleration schemes using widely available repetitive ultraintense femtosecond lasers.These applications not only require high beam energy,but also place demanding requirements on the source stability and controllability.This can be seriously affected by the laser temporal contrast,precluding the replication of ion acceleration performance on independent laser systems with otherwise similar parameters.Here,we present the experimental generation of>60 MeV protons and>30 MeV u-1 carbon ions from sub-micrometre thickness Formvar foils irradiated with laser intensities>1021 Wcm2.Ions are accelerated by an extreme localised space charge field≥30TVm-1,over a million times higher than used in conventional accelerators.The field is formed by a rapid expulsion of electrons from the target bulk due to relativistically induced transparency,in which relativistic corrections to the refractive index enables laser transmission through normally opaque plasma.We replicate the mechanism on two different laser facilities and show that the optimum target thickness decreases with improved laser contrast due to reduced pre-expansion.Our demonstration that energetic ions can be accelerated by this mechanism at different contrast levels relaxes laser requirements and indicates interaction parameters for realising application-specific beam delivery.
文摘We report on the design and characterization of the plasma mirror system installed on the J-KAREN-P laser at the Kansai Photon Science Institute,National Institutes for Quantum Science and Technology.The reflectivity of the single plasma mirror system exceeded 80%.In addition,the temporal contrast was improved by two orders of magnitude at 1 ps before the main pulse.Furthermore,the laser near-field spatial distribution after the plasma mirror was kept constant at plasma mirror fluence of less than 100 kJ/cm^(2).We also present the results of investigating the difference and the fluctuation in energy,pulse width and pointing stability with and without the plasma mirror system.
