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Journal Articles

Time-resolved soft X-ray imaging of femtosecond laser ablation process in metals

Tomita, Takuro*; Nishikino, Masaharu; Hasegawa, Noboru; Minami, Yasuo*; Takei, Ryota*; Baba, Motoyoshi*; Eyama, Tsuyoshi*; Takayoshi, Shodai*; Kaihori, Takeshi*; Morita, Toshimasa; et al.

Journal of Laser Micro/Nanoengineering, 9(2), p.137 - 142, 2014/06

 Times Cited Count:5 Percentile:32.34(Nanoscience & Nanotechnology)

Femtosecond laser ablation processes on platinum, gold, and tungsten were observed by the single shot pump and probe reflective imaging using a soft X-ray laser probe. To avoid the timing error due to the jitter, we adopted a posteriori correction technique by simultaneous measurement of timing between the pump and probe pulses for every single shot, using a soft X-ray streak camera. A clear difference was found in the temporal behavior of the dynamical response of the soft X-ray reflectivity depending on the irradiated laser fluence in these three materials. On the other hand, the narrow dark rings were found in Pt and W, while an additional bright ring was found outside the dark disk in Au. Our result gives the experimental data comparable with various numerical simulations.

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:40 Percentile:96.82(Instruments & Instrumentation)

Journal Articles

Approach towards quasi-monoenergetic laser ion acceleration with doped target

Morita, Toshimasa

Physics of Plasmas, 21(5), p.053104_1 - 053104_8, 2014/05

 Times Cited Count:3 Percentile:17.45(Physics, Fluids & Plasmas)

Ion acceleration by using a laser pulse irradiating a disk target which includes hydrogen and carbon is examined using three-dimensional particle-in-cell simulations. It is shown that over 200 MeV protons can be generated by using a 620 TW, 5$$times10^{21}$$ W/cm$$^2$$ laser pulse. In a polyethylene (CH$$_2$$) target, protons and carbon ions separate and form two layers by radiation pressure acceleration. A strong Coulomb explosion in this situation and Coulomb repulsion of each layer generates high energy protons. A doped target, low density hydrogen within a carbon disk, becomes a double layer target which is comprised of a thin and low density hydrogen disk on the surface of a high-$$Z$$ atom layer. This then generates a quasi-monoenergetic proton beam.

Journal Articles

Observation of the laser-induced surface dynamics using the single-shot soft X-ray laser probe

Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; Morita, Toshimasa; Sasaki, Akira; Terakawa, Kota*; et al.

X-Ray Lasers 2012; Springer Proceedings in Physics, Vol.147, p.117 - 120, 2014/00

 Times Cited Count:0 Percentile:0

We have developed the femto-second laser pump and soft X-ray laser probe system in order to observe the dynamical processes of the femto-second laser ablation. By using this system, we succeed to obtain the temporal evolution of the soft X-ray reflectivity from the laser induced Pt surface. The results lead that the rate of decrease in the reflectivity of the probe beam has a non-linear relation with the pump laser fluence.

Journal Articles

Laser ion acceleration by using the dynamic motion of a target

Morita, Toshimasa

Physics of Plasmas, 20(9), p.093107_1 - 093107_10, 2013/09

 Times Cited Count:4 Percentile:19.64(Physics, Fluids & Plasmas)

The ion acceleration by a hundred TW laser pulse irradiating a double-layer target is examined using three-dimensional particle-in-cell simulations. For a sufficiently high ion charge-to-mass ratio in the first layer of the target, a strongly inhomogeneous expansion of the first layer occurs due to its Coulomb explosion and the onset of the radiation pressure dominant acceleration regime. The time-varying electric potential of the inhomogeneously expanding ion cloud efficiently accelerates protons. Using the optimum material for the first layer and the optimum laser pulse incidence angle one can obtain a high-energy quasimonoenergetic proton beam.

Journal Articles

Proton acceleration due to anisotropic coulomb explosion of a double-layer target irradiated by an intense laser pulse

Morita, Toshimasa; Bulanov, S. V.; Esirkepov, T. Z.; Koga, J. K.; Kando, Masaki

Journal of the Physical Society of Japan, 81(2), p.024501_1 - 024501_6, 2012/02

 Times Cited Count:5 Percentile:40.14(Physics, Multidisciplinary)

It is shown analytically and by three-dimensional particle-in-cell simulations that higher energy protons are obtained by using material with a high charge-to-mass ratio in the first layer of a double-layer target, because a strong Coulomb explosion occurs in such a material. As a result, the protons keep accelerating for a longer time. Using the optimal conditions for the target, it is shown that high energy and high quality protons can be generated.

Journal Articles

Using the Coulomb explosion effect of a first layer on proton acceleration

Morita, Toshimasa; Bulanov, S. V.; Esirkepov, T. Z.; Koga, J. K.; Kando, Masaki

JAEA-Conf 2011-001, p.94 - 96, 2011/03

no abstracts in English

Journal Articles

Effects of the laser pulse irradiation point on a double layer target on the accelerated ion beam parameters

Morita, Toshimasa; Bulanov, S. V.; Esirkepov, T. Z.; Koga, J. K.; Yamagiwa, Mitsuru

AIP Conference Proceedings 1153, p.103 - 112, 2009/07

In proton acceleration by a laser pulse obliquely incident on a double layer target, it is shown by PIC simulations that the energy spread of the generated protons can be reduced by irradiating the laser pulse on to the off-center position of the target. This provides a way to control the proton energy spectrum. The high energy protons are found to come from an area shifted from the initial target center towards the propagation direction of the laser pulse. We show that the high energy protons with much smaller energy spread can be obtained by appropriately adjusting the size and position of the second proton layer.

Journal Articles

Control of energy distribution of the proton beam with an oblique incidence of the laser pulse

Morita, Toshimasa; Bulanov, S. V.; Esirkepov, T. Z.; Koga, J. K.; Yamagiwa, Mitsuru

Physics of Plasmas, 16(3), p.033111_1 - 033111_7, 2009/03

 Times Cited Count:6 Percentile:25.32(Physics, Fluids & Plasmas)

We investigate proton acceleration by a laser pulse obliquely incident on a double layer target via 3D PIC simulations. It is found that the proton beam energy spread changes by the laser irradiation position and it reaches a minimum at certain position. This provides a way to control the proton energy spectrum. We show that by appropriately adjusting the size and position of the second proton layer that high energy protons with much smaller energy spread can be obtained.

Journal Articles

The Effect of laser pulse incidence angle on the proton acceleration from a double-layer target

Morita, Toshimasa; Esirkepov, T. Z.; Koga, J. K.; Yamagiwa, Mitsuru; Bulanov, S. V.

Plasma Physics and Controlled Fusion, 51(2), p.024002_1 - 024002_18, 2009/02

 Times Cited Count:9 Percentile:11.54(Physics, Fluids & Plasmas)

We investigate theoretically and with three dimensional particle-in-cell simulations high quality laser proton acceleration for the oblique incidence of a high intensity laser pulse on a double-layer target. The double-layer target is composed of a high-Z ion layer coated by a thin and narrow hydrogen patch. The highest proton energy gain is achieved at a certain incidence angle at which the fast proton maximum energy is much greater than the case of normal incidence. The fast protons form a tilted bunch which propagates at some angle with the respect to the normal of the target surface, as determined by the proton energy and the incidence angle.

Journal Articles

Proton acceleration by oblique laser pulse incidence on a double-layer target

Morita, Toshimasa; Esirkepov, T. Z.; Bulanov, S. V.; Koga, J. K.; Yamagiwa, Mitsuru

AIP Conference Proceedings 1024, p.114 - 124, 2008/06

We investigate high quality laser proton acceleration with three dimensional particle-in-cell simulations for oblique incidence of the laser pulse on a double-layer target. The double-layer target is composed of a high-Z ion layer coated by a thin and narrow hydrogen patch. The highest proton energy gain is achieved at a certain incidence angle at which the fast proton maximum energy is much grater than the case of normal incidence. The fast protons form a tilted bunch which propagates at some angle with the respect to the normal of the target surface, as determined by the proton energy and the incidence angle.

Journal Articles

Tunable high-energy ion source via oblique laser pulse incident on a double-layer target

Morita, Toshimasa; Esirkepov, T. Z.; Bulanov, S. V.; Koga, J. K.; Yamagiwa, Mitsuru

Physical Review Letters, 100(14), p.145001_1 - 145001_4, 2008/04

 Times Cited Count:33 Percentile:80.48(Physics, Multidisciplinary)

The laser-driven acceleration of high quality proton beams from a double-layer target, comprised of a high-Z ion layer and a thin disk of hydrogen, is investigated with three-dimensional particle-in-cell simulations in the case of oblique incidence of a laser pulse. It is shown that the proton beam energy reaches its maximum at a certain incidence angle of the laser pulse, where it can be much greater than the energy at normal incidence. The proton beam propagates at some angle with respect to the target surface normal, as determined by the proton energy and the incidence angle.

Journal Articles

Characterization of preformed plasmas using a multi-dimensional hydrodynamic simulation code in the study of high-intensity laser-plasma interactions

Sagisaka, Akito; Utsumi, Takayuki*; Daido, Hiroyuki; Ogura, Koichi; Orimo, Satoshi; Takai, Mamiko; Hayashi, Yukio; Mori, Michiaki; Yogo, Akifumi; Kado, Masataka; et al.

Journal of Plasma Physics, 72(6), p.1281 - 1284, 2006/12

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Characterization of preformed plasmas using a hydrodynamic simulation code in the study of high-intensity laser-plasma interactions

Sagisaka, Akito; Utsumi, Takayuki*; Daido, Hiroyuki; Ogura, Koichi; Orimo, Satoshi; Hayashi, Yukio; Takai, Mamiko; Mori, Michiaki; Yogo, Akifumi; Kado, Masataka; et al.

Reza Enerugigaku Kenkyu Senta Heisei-17-Nendo Kyodo Kenkyu Seika Hokokusho (Heisei-17-Nen 4-Gatsu $$sim$$ Heisei-18-Nen 3-Gatsu), p.61 - 62, 2006/07

no abstracts in English

Journal Articles

Characterization of a laser-driven proton beam

Sagisaka, Akito; Daido, Hiroyuki; Fukumi, Atsushi*; Takai, Mamiko; Yogo, Akifumi; Li, Z.*; Ogura, Koichi; Orimo, Satoshi; Hayashi, Yukio; Mori, Michiaki; et al.

Proceedings of RCNP-JAEA Workshop on Nuclear Photon Science "Hadron-nuclear physics probed by photon", p.195 - 200, 2006/00

High energy ions, electrons, and X-ray are generated from ultrashort pulse high-intensity laser-matter interactions. High-energy protons are observed with a thin-foil target irradiated with a high intensity Ti:sapphire laser at the peak intensity of $$sim$$2.7$$times$$10$$^{18}$$ W/cm$$^{2}$$. The maximum proton energy is $$sim$$900 keV.

Oral presentation

Proton generation from a metal thin foil irradiated with a high intensity ultra-short pulse laser

Sagisaka, Akito; Yogo, Akifumi; Daido, Hiroyuki; Fukumi, Atsushi*; Li, Z.*; Ogura, Koichi; Takai, Mamiko; Orimo, Satoshi; Hayashi, Yukio; Mori, Michiaki; et al.

no journal, , 

no abstracts in English

Oral presentation

Proton generation with a high intensity ultra-short pulse laser 1; Preformed plasma dependence

Sagisaka, Akito; Nakamura, Shu; Mori, Michiaki; Daido, Hiroyuki; Fukumi, Atsushi*; Ogura, Koichi; Orimo, Satoshi; Hayashi, Yukio; Takai, Mamiko; Yogo, Akifumi; et al.

no journal, , 

no abstracts in English

Oral presentation

PIC simulation of laser-driven particle acceleration

Morita, Toshimasa; Bulanov, S. V.; Esirkepov, T. Z.; Koga, J. K.; Yamagiwa, Mitsuru

no journal, , 

no abstracts in English

Oral presentation

Direct measurement of the femto-second laser ablation dynamics by using the single-shot soft X-ray laser interferometer, 2

Hasegawa, Noboru; Nishikino, Masaharu; Kaihori, Takeshi*; Hirano, Yusuke; Morita, Toshimasa; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Tomita, Takuro*; Minami, Yasuo*; Terakawa, Kota*; et al.

no journal, , 

no abstracts in English

Oral presentation

Proton acceleration due to Coulomb explosion and the RPDA of a target

Morita, Toshimasa; Bulanov, S. V.; Koga, J. K.

no journal, , 

We study the conditions for generating higher energy protons with a lower power and energy laser. The simulations were performed with a 3D electromagnetic code, based on the PIC method. A laser pulse with a power of 620 TW, energy of 18J and peak intensity of 5$$times$$10$$^{21}$$W/cm$$^{2}$$, irradiates a disk target. The higher energy protons can be obtained by using a "light" material for the first layer. As a result of this, a strong Coulomb explosion occurs and movement of the first layer occurs by RPDA (Radiation Pressure Dominant Acceleration). By using a hydrogen disk target, we obtain a proton beam with an energy of 200 MeV and an energy spread of 2.3% by cutting the proton cloud.

23 (Records 1-20 displayed on this page)