A. Sagisaka
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View article: The role of x-ray self-absorption effects in plasma generated by double-sided irradiation of foil targets with femtosecond laser pulses
The role of x-ray self-absorption effects in plasma generated by double-sided irradiation of foil targets with femtosecond laser pulses Open
In relativistic plasma expansion, a relative motion of plasma components causes absorption of spectral lines to be Doppler-shifted with respect to the emission line centers. The shift of spectral line can be of an order or exceeding the na…
View article: Alloharmonics in Burst Intensification by Singularity Emitting Radiation
Alloharmonics in Burst Intensification by Singularity Emitting Radiation Open
Burst Intensification by Singularity Emitting Radiation (BISER) in underdense relativistic laser plasma is a bright source of coherent extreme ultraviolet (XUV) and x-ray radiation. In contrast to all harmonic generation mechanisms, high-r…
View article: Demonstration of The Brightest Nano-size Gamma Source
Demonstration of The Brightest Nano-size Gamma Source Open
Gamma rays selectively interact with nuclei, induce and mediate nuclear reactions and elementary particle interactions, and exceed x-rays in penetrating power and thus are indispensable for analysis and modification of dense objects. Yet, …
View article: Ultrarelativistic Fe plasma with GJ/cm3 energy density created by femtosecond laser pulses
Ultrarelativistic Fe plasma with GJ/cm3 energy density created by femtosecond laser pulses Open
The generation of a plasma with an ultrahigh energy density of 1.2 GJ/cm3 (which corresponds to about 12 Gbar pressure) is investigated by irradiating thin stainless-steel foils with high-contrast femtosecond laser pulses with relativistic…
View article: Metrology for sub-Rayleigh-length target positioning in ∼10<sup>22</sup> W/cm<sup>2</sup> laser–plasma experiments
Metrology for sub-Rayleigh-length target positioning in ∼10<sup>22</sup> W/cm<sup>2</sup> laser–plasma experiments Open
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 descr…
View article: In-vacuum post-compression of optical probe pulses for relativistic plasma diagnostics
In-vacuum post-compression of optical probe pulses for relativistic plasma diagnostics Open
Ultrafast optical probing is a widely used method of underdense plasma diagnostic. In relativistic plasma, the motion blur limits spatial resolution in the direction of motion. For many high-power lasers the initial pulse duration of 30–50…
View article: In-vacuum post-compression of optical probe pulse for relativistic plasma diagnostics
In-vacuum post-compression of optical probe pulse for relativistic plasma diagnostics Open
Ultrafast optical probing is a widely used method of underdense plasma diagnostic. In relativistic plasma, the motion blur limits spatial resolution in the direction of motion. For many high-power lasers the initial pulse duration of 30-50…
View article: The Role of Collision Ionization of K-Shell Ions in Nonequilibrium Plasmas Produced by the Action of Super Strong, Ultrashort PW-Class Laser Pulses on Micron-Scale Argon Clusters with Intensity up to 5 × 1021 W/cm2
The Role of Collision Ionization of K-Shell Ions in Nonequilibrium Plasmas Produced by the Action of Super Strong, Ultrashort PW-Class Laser Pulses on Micron-Scale Argon Clusters with Intensity up to 5 × 1021 W/cm2 Open
The generation of highly charged ions in laser plasmas is usually associated with collisional ionization processes that occur in electron–ion collisions. An alternative ionization channel caused by tunnel ionization in an optical field is …
View article: Laser Output Performance and Temporal Quality Enhancement at the J-KAREN-P Petawatt Laser Facility
Laser Output Performance and Temporal Quality Enhancement at the J-KAREN-P Petawatt Laser Facility Open
We described the output performance and temporal quality enhancement of the J-KAREN-P petawatt laser facility. After wavefront correction using a deformable mirror, focusing with an f/1.3 off-axis parabolic mirror delivered a peak intensit…
View article: In-vacuum post-compression of low-fluence femtosecond probe laser pulses
In-vacuum post-compression of low-fluence femtosecond probe laser pulses Open
Ultrafast optical probing is a widely used method of underdense plasma diagnostic. In relativistic plasma, the motion blur limits spatial resolution in the direction of motion. For many high-power lasers the initial pulse duration of 30-50…
View article: In-vacuum post-compression of optical probe pulse for relativistic plasma diagnostics
In-vacuum post-compression of optical probe pulse for relativistic plasma diagnostics Open
Ultrafast optical probing is a widely used method of underdense plasma diagnostic. In relativistic plasma, the motion blur limits spatial resolution in the direction of motion. For many high-power lasers the initial pulse duration of 30-50…
View article: Diagnostics for precise target positioning in ~10^22 W/cm2 laser-plasma experiments
Diagnostics for precise target positioning in ~10^22 W/cm2 laser-plasma experiments Open
Tight focusing with very small f-numbers is necessary to achieve highest at-focus irradiances. However, tight focusing also means short Rayleigh length, which imposes strong demands on the precise positioning of the target at the best focu…
View article: High-order alloharmonics produced by nonperiodic drivers
High-order alloharmonics produced by nonperiodic drivers Open
High-order harmonics are ubiquitous in nature and present in electromagnetic, acoustic, and gravitational waves. They are generated by periodic nonlinear processes or periodic high-frequency pulses. However, this periodicity is often inexa…
View article: Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters
Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters Open
View article: Enhanced diagnostics of radiating relativistic singularities and BISER by nonlinear post-compression of optical probe pulse
Enhanced diagnostics of radiating relativistic singularities and BISER by nonlinear post-compression of optical probe pulse Open
The enhancement of the resolution of pump-probe optical diagnostics for ultrafast processes by compressing the probe pulse duration using the CafCA approach [1] is considered on an example of the BISER soft-X-ray generation [2] with the J-…
View article: Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters
Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters Open
Multi-MeV high-purity proton acceleration by using a hydrogen cluster target irradiated with repetitive, relativistic intensity laser pulses has been demonstrated. Statistical analysis of hundreds of data sets highlights the existence of m…
View article: Construction of a Magnetic Bottle Electron Spectrometer for Electron Energy Measurement in BISER X-Rays and Xe Interaction
Construction of a Magnetic Bottle Electron Spectrometer for Electron Energy Measurement in BISER X-Rays and Xe Interaction Open
Quantum science and technology Kansai group has found new harmonics X-ray radiation from the relativistic laser-produced plasma, burst intensification by singularity emitting radiation (BISER). As a next step, the BISER pulse width is one …
View article: Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters
Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters Open
Multi-MeV high-purity proton acceleration by using a hydrogen cluster target irradiated with repetitive, relativistic intensity laser pulses has been demonstrated. Statistical analysis of hundreds of data sets highlights the existence of m…
View article: Characterization of the plasma mirror system at the J-KAREN-P facility
Characterization of the plasma mirror system at the J-KAREN-P facility Open
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…
View article: Enhancement of pre-pulse and picosecond pedestal contrast of the petawatt J-KAREN-P laser
Enhancement of pre-pulse and picosecond pedestal contrast of the petawatt J-KAREN-P laser Open
We have experimentally improved the temporal contrast of the petawatt J-KAREN-P laser facility. We have investigated how the generation of pre-pulses by post-pulses changes due to the temporal overlap between the stretched pulse and the po…
View article: Petawatt Femtosecond Laser Pulses from Titanium-Doped Sapphire Crystal
Petawatt Femtosecond Laser Pulses from Titanium-Doped Sapphire Crystal Open
Ultra-high intensity femtosecond lasers have now become excellent scientific tools for the study of extreme material states in small-scale laboratory settings. The invention of chirped-pulse amplification (CPA) combined with titanium-doped…
View article: Dynamics of laser-driven heavy-ion acceleration clarified by ion charge states
Dynamics of laser-driven heavy-ion acceleration clarified by ion charge states Open
Motivated by the development of next-generation heavy-ion sources, we have investigated the ionization and acceleration dynamics of an ultraintense laser-driven high- Z silver target, experimentally, numerically, and analytically. Using a …
View article: Demonstration of repetitive energetic proton generation by ultra-intense laser interaction with a tape target
Demonstration of repetitive energetic proton generation by ultra-intense laser interaction with a tape target Open
View article: Observation of Burst Intensification by Singularity Emitting Radiation generated from relativistic plasma with a high-intensity laser
Observation of Burst Intensification by Singularity Emitting Radiation generated from relativistic plasma with a high-intensity laser Open
Coherent x-rays via the Burst Intensification by Singularity Emitting Radiation (BISER) mechanism are generated from relativistic plasma in helium gas target. A broad modulation of the BISER spectrum, which is significantly wider than the …
View article: Effect of Small Focus on Electron Heating and Proton Acceleration in Ultrarelativistic Laser-Solid Interactions
Effect of Small Focus on Electron Heating and Proton Acceleration in Ultrarelativistic Laser-Solid Interactions Open
Acceleration of particles from the interaction of ultraintense laser pulses up to 5×10^{21} W cm^{-2} with thin foils is investigated experimentally. The electron beam parameters varied with decreasing spot size, not just laser intensity, …
View article: Discovery of burst intensification by singularity emitting radiation (biser)
Discovery of burst intensification by singularity emitting radiation (biser) Open
View article: Laser Requirements for High-Order Harmonic Generation by Relativistic Plasma Singularities
Laser Requirements for High-Order Harmonic Generation by Relativistic Plasma Singularities Open
We discuss requirements on relativistic-irradiance (I0 > 1018 W/cm2) high-power (multi-terawatt) ultrashort (femtosecond) lasers for efficient generation of high-order harmonics in gas jet targets in a new regime discovered recently (Piroz…
View article: Ultra-intense K-shell emission from stainless steel foils irradiated by femtosecond laser pulses with ultra-high intensity (i ≥ 1021 W/cm2)
Ultra-intense K-shell emission from stainless steel foils irradiated by femtosecond laser pulses with ultra-high intensity (i ≥ 1021 W/cm2) Open
View article: UV Harmonic Generation and Laser-Driven Proton Acceleration from Thin-Foil Target
UV Harmonic Generation and Laser-Driven Proton Acceleration from Thin-Foil Target Open
UV harmonics and protons are observed with a high-intensity Ti:sapphire laser. High-energy protons are generated with an aluminum thin-foil target. Simultaneously with the high-energy protons the generation of third- and fourth-order harmo…
View article: The J-KAREN-P Facility Laser Performance Status
The J-KAREN-P Facility Laser Performance Status Open
The OPCPA/Ti:sapphire hybrid laser system (named J-KAREN-P laser system) is an infrastructure aiming to realize experiments achieving 1022 W/cm2 at 0.1 Hz. 63 J broadband pulse energies at 0.1 Hz, 30 fs compressed pulse duration, and ~1012…