The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the under...The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the underlying physics and regular procedure of such a measurement through the radioactivation of a stack composed of aluminum,copper,and CR-39 plates as well as radiochromic films(RCFs).After being radioactivated,the copper plates are placed on imaging plates(IPs)to detect the positrons emitted by the reaction products through contact imaging.The spectrum and energy-dependent spatial profile of the protons are then obtained from the IPs and confirmed by the measured ones from the RCFs and CR-39 plates.We also discuss the detection range,influence of electrons,radiation safety,and spatial resolution of this measurement.Finally,insights regarding the extension of the current method to online measurements and dynamic proton imaging are also provided.展开更多
The intensity attenuation of a high-power laser is a frequent task in the measurements of optical science.Laser intensity can be attenuated by inserting an optical element,such as a partial reflector,polarizer or abso...The intensity attenuation of a high-power laser is a frequent task in the measurements of optical science.Laser intensity can be attenuated by inserting an optical element,such as a partial reflector,polarizer or absorption filter.These devices are,however,not always easily applicable,especially in the case of ultra-high-power lasers,because they can alter the characteristics of a laser beam or become easily damaged.In this study,we demonstrated that the intensity of a laser beam could be effectively attenuated using a random pinhole attenuator(RPA),a device with randomly distributed pinholes,without changing the beam properties.With this device,a multi-PW laser beam was successfully attenuated and the focused beam profile was measured without any alterations of its characteristics.In addition,it was confirmed that the temporal profile of a laser pulse,including the spectral phase,was preserved.Consequently,the RPA possesses significant potential for a wide range of applications.展开更多
In the 2015 review paper‘Petawatt Class Lasers Worldwide’a comprehensive overview of the current status of highpower facilities of>200 TW was presented.This was largely based on facility specifications,with some ...In the 2015 review paper‘Petawatt Class Lasers Worldwide’a comprehensive overview of the current status of highpower facilities of>200 TW was presented.This was largely based on facility specifications,with some description of their uses,for instance in fundamental ultra-high-intensity interactions,secondary source generation,and inertial confinement fusion(ICF).With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification(CPA),which made these lasers possible,we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed.We are now in the era of multi-petawatt facilities coming online,with 100 PW lasers being proposed and even under construction.In addition to this there is a pull towards development of industrial and multi-disciplinary applications,which demands much higher repetition rates,delivering high-average powers with higher efficiencies and the use of alternative wavelengths:mid-IR facilities.So apart from a comprehensive update of the current global status,we want to look at what technologies are to be deployed to get to these new regimes,and some of the critical issues facing their development.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
High-power terahertz radiation was observed to be emitted from a gas jet irradiated by 100-terawatt-class laser pulses in the laser-wakefield acceleration of electrons.The emitted terahertz radiation was characterized...High-power terahertz radiation was observed to be emitted from a gas jet irradiated by 100-terawatt-class laser pulses in the laser-wakefield acceleration of electrons.The emitted terahertz radiation was characterized in terms of its spectrum,polarization,and energy dependence on the accompanying electron bunch energy and charge under various gas target conditions.With a nitrogen target,more than 4 mJ of energy Was produced at<10 THz with a laser-to-terahertz conversion efficiency of~0.15%.Such strong terahertz radiation is hypothesized to be produced from plasma electrons accelerated by the ponderomotive force of the laser and the plasma wakefelds on the time scale of the laser pulse duration and plasma period.This model is examined with analytic calculations and particle-in-cell simulations to better understand the generation mechanism of high-energy terahertz radiation in laser-wakefield acceleration.展开更多
Deep learning has been widely and actively used in various research areas.Recently,in gauge/gravity duality,a new deep learning technique called AdS/DL(Deep Learning)has been proposed.The goal of this paper is to expl...Deep learning has been widely and actively used in various research areas.Recently,in gauge/gravity duality,a new deep learning technique called AdS/DL(Deep Learning)has been proposed.The goal of this paper is to explain the essence of AdS/DL in the simplest possible setups,without resorting to knowledge of gauge/gravity duality.This perspective will be useful for various physics problems:from the emergent spacetime as a neural network to classical mechanics problems.For prototypical examples,we choose simple classical mechanics problems.This method is slightly different from standard deep learning techniques in the sense that we not only have the right final answers but also obtain physical understanding of learning parameters.展开更多
基金supported by the Institute for Basic ScienceKorea under the project code IBS-R012-D1by the Ultrashort Quantum Beam Facility(UQBF)operation program(No.140011)through APRI,GIST。
文摘The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the underlying physics and regular procedure of such a measurement through the radioactivation of a stack composed of aluminum,copper,and CR-39 plates as well as radiochromic films(RCFs).After being radioactivated,the copper plates are placed on imaging plates(IPs)to detect the positrons emitted by the reaction products through contact imaging.The spectrum and energy-dependent spatial profile of the protons are then obtained from the IPs and confirmed by the measured ones from the RCFs and CR-39 plates.We also discuss the detection range,influence of electrons,radiation safety,and spatial resolution of this measurement.Finally,insights regarding the extension of the current method to online measurements and dynamic proton imaging are also provided.
基金supported by an Institute for Basic Science grant(IBS-R012-D1)a National Research Foundation of Korea(NRF)grant funded by the Korea government(MIST)(No.2022R1A2C3006025 and No.RS-2023-00218180)。
文摘The intensity attenuation of a high-power laser is a frequent task in the measurements of optical science.Laser intensity can be attenuated by inserting an optical element,such as a partial reflector,polarizer or absorption filter.These devices are,however,not always easily applicable,especially in the case of ultra-high-power lasers,because they can alter the characteristics of a laser beam or become easily damaged.In this study,we demonstrated that the intensity of a laser beam could be effectively attenuated using a random pinhole attenuator(RPA),a device with randomly distributed pinholes,without changing the beam properties.With this device,a multi-PW laser beam was successfully attenuated and the focused beam profile was measured without any alterations of its characteristics.In addition,it was confirmed that the temporal profile of a laser pulse,including the spectral phase,was preserved.Consequently,the RPA possesses significant potential for a wide range of applications.
文摘In the 2015 review paper‘Petawatt Class Lasers Worldwide’a comprehensive overview of the current status of highpower facilities of>200 TW was presented.This was largely based on facility specifications,with some description of their uses,for instance in fundamental ultra-high-intensity interactions,secondary source generation,and inertial confinement fusion(ICF).With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification(CPA),which made these lasers possible,we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed.We are now in the era of multi-petawatt facilities coming online,with 100 PW lasers being proposed and even under construction.In addition to this there is a pull towards development of industrial and multi-disciplinary applications,which demands much higher repetition rates,delivering high-average powers with higher efficiencies and the use of alternative wavelengths:mid-IR facilities.So apart from a comprehensive update of the current global status,we want to look at what technologies are to be deployed to get to these new regimes,and some of the critical issues facing their development.
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.
基金This work was supported by Institute for Basic Science under IBS-RO12-D1.
文摘High-power terahertz radiation was observed to be emitted from a gas jet irradiated by 100-terawatt-class laser pulses in the laser-wakefield acceleration of electrons.The emitted terahertz radiation was characterized in terms of its spectrum,polarization,and energy dependence on the accompanying electron bunch energy and charge under various gas target conditions.With a nitrogen target,more than 4 mJ of energy Was produced at<10 THz with a laser-to-terahertz conversion efficiency of~0.15%.Such strong terahertz radiation is hypothesized to be produced from plasma electrons accelerated by the ponderomotive force of the laser and the plasma wakefelds on the time scale of the laser pulse duration and plasma period.This model is examined with analytic calculations and particle-in-cell simulations to better understand the generation mechanism of high-energy terahertz radiation in laser-wakefield acceleration.
基金Supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of ScienceICT&Future Planning(NRF-2017R1A2B4004810,NRF-2021R1A2C1006791)the GIST Research Institute(GRI)grant funded by GIST in 2021。
文摘Deep learning has been widely and actively used in various research areas.Recently,in gauge/gravity duality,a new deep learning technique called AdS/DL(Deep Learning)has been proposed.The goal of this paper is to explain the essence of AdS/DL in the simplest possible setups,without resorting to knowledge of gauge/gravity duality.This perspective will be useful for various physics problems:from the emergent spacetime as a neural network to classical mechanics problems.For prototypical examples,we choose simple classical mechanics problems.This method is slightly different from standard deep learning techniques in the sense that we not only have the right final answers but also obtain physical understanding of learning parameters.
