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Journal Articles

Prepulse and amplified spontaneous emission effects on the interaction of a petawatt class laser with thin solid targets

Esirkepov, T. Z.; Koga, J. K.; Sunahara, Atsushi*; Morita, Toshimasa; Nishikino, Masaharu; Kageyama, Kei*; Nagatomo, Hideo*; Nishihara, Katsunobu; Sagisaka, Akito; Kotaki, Hideyuki; et al.

Nuclear Instruments and Methods in Physics Research A, 745, p.150 - 163, 2014/05

 Times Cited Count:32 Percentile:2.77(Instruments & Instrumentation)

Journal Articles

Stabilization of radiation reaction with vacuum polarization

Seto, Keita*; Zhang, S.*; Koga, J. K.; Nagatomo, Hideo*; Nakai, Mitsuo*; Mima, Kunioki*

Progress of Theoretical and Experimental Physics (Internet), 2014(4), p.043A01_1 - 043A01_10, 2014/04

 Times Cited Count:9 Percentile:37.04(Physics, Multidisciplinary)

Journal Articles

Theoretical study of ultrarelativistic laser-electron interaction with radiation reaction

Seto, Keita*; Nagatomo, Hideo*; Koga, J. K.; Taguchi, Toshihiro*; Mima, Kunioki*

EPJ Web of Conferences (Internet), 59, p.17020_1 - 17020_4, 2013/11

 Times Cited Count:0 Percentile:100

Journal Articles

Radiation reaction in ultrarelativistic laser-spinning electron interactions

Seto, Keita*; Nagatomo, Hideo*; Koga, J. K.; Mima, Kunioki*

Progress of Theoretical and Experimental Physics (Internet), 2013(5), p.053A01_1 - 053A01_10, 2013/05

 Times Cited Count:1 Percentile:86.3(Physics, Multidisciplinary)

Journal Articles

Theoretical study of ultra-relativistic laser electron interaction with radiation reaction by quantum description

Seto, Keita*; Nagatomo, Hideo*; Koga, J. K.; Mima, Kunioki*

Plasma and Fusion Research (Internet), 7(Sp.1), p.2404010_1 - 2404010_4, 2012/02

Journal Articles

Equation of motion with radiation reaction in ultrarelativistic laser-electron interactions

Seto, Keita*; Nagatomo, Hideo*; Koga, J. K.; Mima, Kunioki*

Physics of Plasmas, 18(12), p.123101_1 - 123101_8, 2011/12

 Times Cited Count:9 Percentile:55.23(Physics, Fluids & Plasmas)

Journal Articles

Laser-driven proton generation with a thin-foil target

Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Ma, J.*; Kiriyama, Hiromitsu; Kanazawa, Shuhei; et al.

NIFS-PROC-85, p.30 - 33, 2011/02

The experiment of proton generation is performed for developing the laser-driven ion source. We observe proton signals in the laser-plasma interaction by using a thin-foil target. To get higher energy protons the size of the preformed plasma is reduced by changing the laser contrast level. In the high-contrast laser pulse case the maximum energy of the protons generated at rear side of the target increases.

Journal Articles

FIREX project and effects of self-generated electric and magnetic fields on electron-driven fast ignition

Mima, Kunioki*; Sunahara, Atsushi*; Shiraga, Hiroyuki*; Nishimura, Hiroaki*; Azechi, Hiroshi*; Nakamura, Tatsufumi; Jozaki, Tomoyuki*; Nagatomo, Hideo*; Garcia, C.*; Veralde, P.*

Plasma Physics and Controlled Fusion, 52(12), p.124047_1 - 124047_6, 2010/12

 Times Cited Count:9 Percentile:60.18(Physics, Fluids & Plasmas)

Fast ignition is a new scheme in laser fusion, in which higher energy gain with a smaller laser pulse energy is expected. At Osaka University, a laser with four beams and a total output of 10 kJ ps-1, laser for fast ignition experiment (LFEX), has been constructed and we have carried out an integrated experiment with one beam of the LFEX. Through experiments it was found that the coupling efficiency is degraded when the laser pre-pulse is not sufficiently small. Furthermore, the distance between the hot electron source and the core plasma is large. In this paper it is proposed that a thin foil covers the laser entrance of the cone to mitigate the pre-plasma and a double cone reduces the loss of high energy electrons from the side wall of the cone. The simulations indicate that a higher coupling efficiency is expected for the double cone target with a thin foil at the laser entrance.

Journal Articles

Proton generation and terahertz radiation from a thin-foil target with a high-intensity laser

Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Ma, J.*; Kiriyama, Hiromitsu; Kanazawa, Shuhei; et al.

Reza Kenkyu, 38(9), p.702 - 705, 2010/09

High-intensity laser and thin-foil interactions produce high-energy particles, hard X-ray, high-order harmonics, and terahertz (THz) radiation. A proton beam driven by a high-intensity laser has received attention as a compact ion source for medical applications. In this study we have tested simultaneous generation of protons and THz radiation from a thin-foil target. We use a Ti:sapphire laser system (J-KAREN) at JAEA. A laser beam is focused by an off-axis parabolic mirror at the thin-foil target. We observed the high-energy proton in the rear side of the target and THz radiation in the reflected direction. Next, high energy protons are observed by reducing the size of preformed plasma.

Journal Articles

Control of laser-accelerated proton beams by modifying the target density with ASE

Yogo, Akifumi; Kiriyama, Hiromitsu; Mori, Michiaki; Esirkepov, T. Z.; Ogura, Koichi; Sagisaka, Akito; Orimo, Satoshi; Nishiuchi, Mamiko; Pirozhkov, A. S.; Nagatomo, Hideo*; et al.

European Physical Journal D, 55(2), p.421 - 425, 2009/11

 Times Cited Count:3 Percentile:77.55(Optics)

We demonstrate the laser-ion acceleration from a near-critical density plasma, when amplified spontaneous emission (ASE) was used to convert a solid foil target into the lower-density target. In this work, a direct comparison is made by changing the ASE intensity by factor 3 in order to investigate the target density-dependency of the laser-ion acceleration. The beam direction of high-energy component is successfully controlled by modifying the target density. The near-critical density plasma can be a favorable target to control the beam direction to be dependent on its energy.

Journal Articles

Observation of UV harmonics from a thin-foil target in the high-intensity laser-driven proton generation

Sagisaka, Akito; Pirozhkov, A. S.; Ma, J.-L.; Mori, Michiaki; Yogo, Akifumi; Ogura, Koichi; Orimo, Satoshi; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Kanazawa, Shuhei; et al.

Journal of Plasma and Fusion Research SERIES, Vol.8, p.464 - 467, 2009/09

We measure the UV harmonics from a thin-foil target by changing the laser pulse duration in the high-energy proton generation. The maximum proton energies are around 1 MeV. In the case of the $$sim$$500 fs, the peaks of UV harmonics up to fourth-order clearly appear. The spectra are broadened and shifted at the pulse durations of $$sim$$100 fs and $$sim$$30 fs.

Journal Articles

Experimental and computational characterization of hydrodynamic expansion of a preformed plasma from thin-foil target for laser-driven proton acceleration

Sagisaka, Akito; Nagatomo, Hideo*; Daido, Hiroyuki; Pirozhkov, A. S.; Ogura, Koichi; Orimo, Satoshi; Mori, Michiaki; Nishiuchi, Mamiko; Yogo, Akifumi; Kado, Masataka

Journal of Plasma Physics, 75(5), p.609 - 617, 2009/06

 Times Cited Count:5 Percentile:76.39(Physics, Fluids & Plasmas)

We characterize the electron density distributions of preformed plasma for laser-accelerated proton generation. The preformed plasma of a thin-foil target is generated by prepulse and ASE of a high-intensity Ti:sapphire laser and is measured with an interferometer using a second harmonic probe beam. High-energy protons are obtained by reducing the size of the preformed plasma by changing the ASE duration before main pulse at the front side of the target. Simulation results with two-dimensional radiation hydrodynamic code are close to the experimental results for low-density region $$sim$$4$$times$$10$$^{19}$$ cm$$^{-3}$$ at the front side.

Journal Articles

Ion acceleration using temporally-controlled high-intensity laser pulses

Yogo, Akifumi; Daido, Hiroyuki; Mori, Michiaki; Kiriyama, Hiromitsu; Bulanov, S. V.; Bolton, P.; Esirkepov, T. Z.; Ogura, Koichi; Sagisaka, Akito; Orimo, Satoshi; et al.

Reza Kenkyu, 37(6), p.449 - 454, 2009/06

The acceleration of protons driven by a high-intensity laser is comprehensively investigated via control of the target density by using ASE just before the time of the main-laser interaction. Two cases were investigated for which the ASE intensity differed by three orders of magnitude: In the low contrast case the beam centre for higher energy protons is shifted closer to the laser-propagation direction of 45$$^{circ}$$, while the center of lower-energy beam remains near the target normal direction. Particle-in-cell simulations reveal that the characteristic proton acceleration is due to the quasistatic magnetic field on the target rear side with the magnetic pressure sustaining a charge separation electrostatic field.

Journal Articles

Probing of nonlinear evolution of laser wakefield by Raman scattering of laser light

Zhou, W.*; Mima, Kunioki*; Nakamura, Tatsufumi; Nagatomo, Hideo*

Physics of Plasmas, 15(9), p.093107_1 - 093107_6, 2008/09

 Times Cited Count:7 Percentile:67.52(Physics, Fluids & Plasmas)

When a weak probe laser pulse is injected into a wakefield excited by a short high-intensity pump laser pulse, the probe pulse will be Raman scattered by the wakefield. It is possible to determine the density profile from the spectrum of this forward Raman scattered probe laser. In previous research, an analytical solution for the multiple sidebands of the forward Raman scattering of the probe laser pulse was presented. These multiple sidebands are connected with the steepening of density perturbation of the wakefield. More detailed information of the probe pulse in wakefield is studied with one-dimensional particle-in-cell simulations. The analytical solution and the results of simulation are consistent with each other and other experiments.

Journal Articles

Efficient production of a collimated MeV proton beam from a Polyimide target driven by an intense femtosecond laser pulse

Nishiuchi, Mamiko; Daido, Hiroyuki; Yogo, Akifumi; Orimo, Satoshi; Ogura, Koichi; Ma, J.-L.; Sagisaka, Akito; Mori, Michiaki; Pirozhkov, A. S.; Kiriyama, Hiromitsu; et al.

Physics of Plasmas, 15(5), p.053104_1 - 053104_10, 2008/05

 Times Cited Count:38 Percentile:14.73(Physics, Fluids & Plasmas)

High-flux energetic protons whose maximum energies are up to 4 MeV are generated by an intense femtosecond Titanium Sapphire laser pulse interacting with a 7.5, 12.5, and 25$$mu$$m thick Polyimide tape targets. The laser pulse energy is 1.7 J, duration is 34 fs, and intensity is 3$$times$$10$$^{19}$$Wcm$$^{-2}$$. The amplified spontaneous emission (ASE) has the intensity contrast ratio of 4$$times$$10$$^{-8}$$. The conversion efficiency from laser energy into proton kinetic energies of $$sim$$3% is achieved, which is comparable or even higher than those achieved in the previous works with nanometer-thick targets and the ultrahigh contrast laser pulses ($$sim$$10$$^{-10}$$).

Journal Articles

Laser ion acceleration via control of the near-critical density target

Yogo, Akifumi; Daido, Hiroyuki; Bulanov, S. V.; Nemoto, Koshichi*; Oishi, Yuji*; Nayuki, Takuya*; Fujii, Takashi*; Ogura, Koichi; Orimo, Satoshi; Sagisaka, Akito; et al.

Physical Review E, 77(1), p.016401_1 - 016401_6, 2008/01

 Times Cited Count:95 Percentile:2.33(Physics, Fluids & Plasmas)

The duration-controlled amplified spontaneous emission with intensity of $$10^{13}$$ W/cm$$^2$$ is used to convert a 7.5 $$mu$$m thick polyimide foil into a near-critical plasma, in which the $$p$$-polarized, 45 fs, $$10^{19}$$ W/cm$$^2$$ laser pulse generates 3.8 MeV protons, emitted at some angle between the target normal and the laser propagation direction of 45$$^{circ}$$. Particle-in-cell simulations reveal that the efficient proton acceleration is due to generation of the quasistatic magnetic field on the target rear side with the magnetic pressure inducing and sustaining a charge separation electrostatic field.

Journal Articles

Laser-driven proton acceleration from a near-critical density target

Yogo, Akifumi; Daido, Hiroyuki; Bulanov, S. V.; Esirkepov, T. Z.; Nemoto, Koshichi*; Oishi, Yuji*; Nayuki, Takuya*; Fujii, Takashi*; Ogura, Koichi; Orimo, Satoshi; et al.

Journal of Physics; Conference Series, 112, p.042034_1 - 042034_4, 2008/00

 Times Cited Count:1 Percentile:40.32

In this work, we present a new method to enhance the proton generation by a 10$$^5$$-contrast laser. High-energy protons up to 3.8 MeV are observed with 7.5-$$mu$$m-thick insulator (Polyimide) target irradiated by a laser pulse having energy of 0.8 J and an intensity of 10$$^{19}$$-W/cm$$^2$$. Using two time-of-flight (TOF) spectrometers simultaneously in different directions, we measure the direction dependency of proton-energy spectra. As a result, we find that high-energy component of proton beam is shifted away from the target normal toward the laser-propagation direction, when the laser is focused with 45$$^{circ}$$ incident angle. The TOF measurements over 130 laser shots confirm that the generation of the high-energy protons, which are steered away from the target normal, depends strongly on the laser-focusing condition.

Journal Articles

Optimization of cone target geometry for fast ignition

Nakamura, Tatsufumi*; Sakagami, Hitoshi*; Jozaki, Tomoyuki*; Nagatomo, Hideo*; Mima, Kunioki*; Koga, J. K.

Physics of Plasmas, 14(10), p.103105_1 - 103105_7, 2007/10

 Times Cited Count:66 Percentile:7.09(Physics, Fluids & Plasmas)

Journal Articles

High energy electron generation by laser-cone interaction

Nakamura, Tatsufumi*; Sakagami, Hitoshi*; Jozaki, Tomoyuki*; Nagatomo, Hideo*; Mima, Kunioki*; Koga, J. K.

Plasma and Fusion Research (Internet), 2, p.018_1 - 018_6, 2007/05

Electron acceleration processes taking place in the interaction of ultra-intense laser pulses with cone targets are studied by using two-dimensional Particle-in-Cell (PIC) simulations to understand the characteristics of electrons generated from cone targets. It is explained that there are two dominant acceleration processes which are distinctive in the laser-cone interaction. One is the acceleration and transport along the side wall of the cone target, where electrons are guided along the side wall surface towards the cone tip by surface magnetic and electric fields. The second is the ponderomotive acceleration at the cone tip by the laser field which is intensified by cone focusing. The understanding of these acceleration processes helps to design cone targets to control the electron energy characteristics.

Journal Articles

Characterization of thin-foil preformed plasmas for high-intensity laser plasma interactions

Sagisaka, Akito; Daido, Hiroyuki; Pirozhkov, A. S.; Ogura, Koichi; Orimo, Satoshi; Mori, Michiaki; Nishiuchi, Mamiko; Yogo, Akifumi; Kado, Masataka; Nakamura, Shu*; et al.

Acta Physica Hungarica B, 26(3-4), p.327 - 333, 2006/00

no abstracts in English

34 (Records 1-20 displayed on this page)