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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：43 Percentile：96.7(Instruments & Instrumentation)Lobet, M.*; Kando, Masaki; Koga, J. K.; Esirkepov, T. Z.; Nakamura, Tatsufumi; Pirozhkov, A. S.; Bulanov, S. V.
Physics Letters A, 377, p.1114 - 1118, 2013/06
Times Cited Count：13 Percentile：63.45(Physics, Multidisciplinary)A method for the controlled generation of intense high frequency electromagnetic fields by a breaking Langmuir wave (relativistic flying mirrors) in a gradually inhomogeneous plasma is proposed. The wave breaking threshold depends on the local plasma density gradient. Compression, chirping and frequency multiplication of an electromagnetic wave reflected from relativistic mirrors is demonstrated using Particle-In-Cell simulations. Adjusting the shape of the density profile enables control of the reflected light properties.
Bulanov, S. V.; Esirkepov, T. Z.; Kando, Masaki; Koga, J. K.; Nakamura, Tatsufumi; Bulanov, S. S.*; Zhidkov, A.*; Kato, Yoshiaki; Korn, G.*
High-Power, High-Energy, and High-Intensity Laser Technology; and Research Using Extreme Light: Entering New Frontiers with Petawatt-Class Lasers (Proceedings of SPIE, Vol.8780), p.878015_1 - 878015_15, 2013/05
Times Cited Count：9 Percentile：96.34Bulanov, S. V.; Esirkepov, T. Z.; Kando, Masaki; Koga, J. K.; Pirozhkov, A. S.; Nakamura, Tatsufumi; Bulanov, S. S.*; Schroeder, C. B.*; Esarey, E.*; Califano, F.*; et al.
Physics of Plasmas, 19(11), p.113102_1 - 113102_14, 2012/11
Times Cited Count：18 Percentile：62.72(Physics, Fluids & Plasmas)Bulanov, S. V.; Esirkepov, T. Z.; Kando, Masaki; Koga, J. K.; Pirozhkov, A. S.; Nakamura, Tatsufumi; Bulanov, S. S.*; Schroeder, C. B.*; Esarey, E.*; Califano, F.*; et al.
Physics of Plasmas, 19(11), p.113103_1 - 113103_7, 2012/11
Times Cited Count：14 Percentile：54.03(Physics, Fluids & Plasmas)Kando, Masaki; Pirozhkov, A. S.; Nakamura, Tatsufumi; Hayashi, Yukio; Kotaki, Hideyuki; Kawase, Keigo*; Esirkepov, T. Z.; Fukuda, Yuji; Kiriyama, Hiromitsu; Okada, Hajime; et al.
AIP Conference Proceedings 1465, p.159 - 166, 2012/07
Times Cited Count：0 Percentile：0.13
-ray flash generation in ultraintense laser-plasma interactionsNakamura, Tatsufumi; Koga, J. K.; Esirkepov, T. Z.; Kando, Masaki; Korn, G.*; Bulanov, S. V.
Physical Review Letters, 108(19), p.195001_1 - 195001_5, 2012/05
Times Cited Count：166 Percentile：97.56(Physics, Multidisciplinary)When high-intensity laser interaction with matter enters the regime of dominated radiation reaction, the radiation losses open the way for producing short pulse high power ray flashes. The -ray pulse duration and divergence are determined by the laser pulse amplitude and by the plasma target density scale length. On the basis of theoretical analysis and particle-in-cell simulations with the radiation friction force incorporated, optimal conditions for generating a -ray flash with a tailored overcritical density target are found.
Kando, Masaki; Nakamura, Tatsufumi; Pirozhkov, A. S.; Esirkepov, T. Z.; Koga, J. K.; Bulanov, S. V.
Progress of Theoretical Physics Supplement, (193), p.236 - 242, 2012/05
Nakamura, Tatsufumi
Purazuma, Kaku Yugo Gakkai-Shi, 88(1), p.18 - 20, 2012/01
We have proposed a magnetic vortex acceleration mechanism, which utilizes magnetic dipole vortex for high energy ion generation. The magnetic dipole vortex is formed inside a near-critical density plasma irradiated by intense short laser pulse. We explain the motion of the generated magnetic dipole vortex and its relation to the high energy ion generation. The energy scaling of accelerated ion is obtained, which predicts 200 MeV protons could be generated by using 100 TW laser pulse.
Hayashi, Yukio; Pirozhkov, A. S.; Kando, Masaki; Fukuda, Yuji; Faenov, A.*; Kawase, Keigo*; Pikuz, T.*; Nakamura, Tatsufumi; Kiriyama, Hiromitsu; Okada, Hajime; et al.
Optics Letters, 36(9), p.1614 - 1616, 2011/05
Times Cited Count：22 Percentile：72.26(Optics)The interaction between a 25 TW laser and Xe clusters at a peak intensity of 1
10
W/cm
has been investigated. Xe K-shell X-rays, whose energies are approximately 30 keV, were clearly observed with a hard X-ray charge-coupled device (X-ray CCD) at 3.4 MPa. Moreover, we studied the yield of the Xe K-shell X-rays by changing the pulse duration of the laser at a constant laser energy, and found that the pulse duration of 40 fs is better than that of 300 fs for generating Xe K-shell X-rays.
Fukuda, Yuji; Faenov, A.*; Tampo, Motonobu; Pikuz, T.*; Nakamura, Tatsufumi; Kando, Masaki; Hayashi, Yukio; Yogo, Akifumi; Sakaki, Hironao; Kameshima, Takashi*; et al.
Progress in Ultrafast Intense Laser Science VII, p.225 - 240, 2011/05
http://www.springer.com/physics/atomic,+molecular,+optical+%26+plasma+physics/book/978-3-642-18326-3We present substantial enhancement of the accelerated ion energies up to 10-20 MeV per nucleon by utilizing the unique properties of the cluster-gas target irradiated with 40-fs laser pulses of only 150 mJ energy, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using thin foil targets. A particle-in-cell simulation infers that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in sub-critical density plasmas. The demonstrated method can be important in the development of efficient laser ion accelerators for hadron therapy and other applications.
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：35.22(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.
Nakamura, Tatsufumi; Tampo, Motonobu; Kodama, Ryosuke*; Bulanov, S. V.; Kando, Masaki
Physics of Plasmas, 17(11), p.113107_1 - 113107_6, 2010/11
Times Cited Count：39 Percentile：82.36(Physics, Fluids & Plasmas)Interactions of high contrast laser pulses with foam-attached targets are investigated via Particle-in-Cell (PIC) simulations in order to enhance the energy coupling from laser to plasmas. A foam layer whose mass density is much lower than that of the solid state is used for controlling the plasma density distribution of the laser irradiation region with the aid of the high contrast laser pulses. The ionization process plays a role in the laser and foam interaction, which results in the formation of periodic structure of ion charge density. The bulk electrons inside the foam layer are heated by the laser pulse, which results in the generation of abundant MeV electrons and higher energy coupling from laser to plasma. These features are utilized for laser ion acceleration by using a foam-attached thin foil target. It is shown that the laser accelerated ion energy is enhanced by properly choosing the foam parameters.
Nakamura, Tatsufumi; Bulanov, S. V.; Esirkepov, T. Z.; Kando, Masaki
Physical Review Letters, 105(13), p.135002_1 - 135002_4, 2010/09
Times Cited Count：134 Percentile：95.72(Physics, Multidisciplinary)Ultraintense laser pulses propagating in near-critical density plasmas generate magnetic dipole vortex structures. In the region of decreasing plasma density, the vortex expands both in forward and lateral directions. The magnetic field pressure pushes electrons and ions to form a density jump along the vortex axis, and induces a longitudinal electric field. This structure moves together with the expanding dipole vortex. The background ions located ahead of the electric field are accelerated to high energies. The energy scaling of ions generated by this magnetic vortex acceleration mechanism is derived and corroborated using Particle-in-Cell (PIC) simulations.
Ter-Avetisyan, S.*; Schn
rer, M.*; Nickles, P. V.*; Sandner, W.*; Borghesi, M.*; Nakamura, Tatsufumi; Mima, Kunioki*
Physics of Plasmas, 17(6), p.063101_1 - 063101_6, 2010/06
Times Cited Count：8 Percentile：31.84(Physics, Fluids & Plasmas)Using a multichannel Thomson spectrometer we have implemented a tomographic approach allowing the reconstruction of the emission characteristics of a laser driven proton source with high energy and spatial resolution. The results demonstrate the complexity of the temporal and spatial characteristics of such a source. The emitted proton beam, which is laminar and divergent ant high energies, becomes convergent at low energies. This implies that a fraction of the proton beam having this kinetic energy is emitted in a collimated way from the target at the turning point between these tow behaviors. Only a finite fraction of the target surface is contributing to the ion spectrum, which is measured at a specific angle within the beam cone. Therefore the momentum distribution of the protons in the emitted beam at any point in space can be controlled by determining the proton source area.
Nakamura, Tatsufumi; Fukuda, Yuji; Kishimoto, Yasuaki*
Physical Review A, 80(5), p.053202_1 - 053202_6, 2009/11
Times Cited Count：14 Percentile：57.19(Optics)Interactions of X-ray free electron laser (XFEL) light with a single cluster target are numerically investigated by using a three-dimensional Particle-in-Cell code. The plasma dynamics as well as relevant atomic processes are taken into account, such as photo-ionization, the Auger effect, collisional ionization/relaxation, and field ionization. It is found that as the XFEL intensity increases to as high as 
photons/pulse/mm, the field ionization, which is the dominant ionization process over the other atomic processes, leads to rapid target ionization. The target damage due to the irradiation by XFEL light is numerically evaluated, which gives an estimation of the XFEL intensity so as to suppress the target damage within a tolerable range for imaging.
Nakamura, Tatsufumi; Fukuda, Yuji; Yogo, Akifumi; Tampo, Motonobu; Kando, Masaki; Hayashi, Yukio; Kameshima, Takashi*; Pirozhkov, A. S.; Esirkepov, T. Z.; Pikuz, T. A.*; et al.
Physics of Plasmas, 16(11), p.113106_1 - 113106_8, 2009/11
Times Cited Count：16 Percentile：53.98(Physics, Fluids & Plasmas)Generation of high energy negative ions from laser plasmas by Coulomb implosion mechanism is investigated. When clusters or underdense plasmas are irradiated by an intense laser pulse, positive ions are accelerated inside the clusters or in the self-focusing channel by the Coulomb explosion. This could lead to the acceleration of negative ions towards target center. The maximum energy of negative ions is typically several times lower than that of positive ions. A theoretical description and corresponding Particle-in-Cell simulations of Coulomb implosion mechanism are presented. We show the evidence of the negative ion acceleration observed in our experiments using high intensity laser pulse and the cluster-gas targets.
Fukuda, Yuji; Faenov, A. Y.; Tampo, Motonobu; Pikuz, T. A.*; Nakamura, Tatsufumi; Kando, Masaki; Hayashi, Yukio; Yogo, Akifumi; Sakaki, Hironao; Kameshima, Takashi*; et al.
Physical Review Letters, 103(16), p.165002_1 - 165002_4, 2009/10
Times Cited Count：157 Percentile：96.73(Physics, Multidisciplinary)A new approach for accelerating ions, based on the use of a cluster-gas target and a compact ultrashort pulse laser, is presented. It is shown that ions with energy 10-20 MeV per nucleon having a small divergence (full angle) of 3.4
are generated, corresponding to an approximately tenfold increase in the ion energies compared to previous experiments using solid targets. It is inferred from a particle-in-cell code simulation that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in near-critical density plasmas.
Faenov, A. Y.; Pikuz, T. A.*; Fukuda, Yuji; Kando, Masaki; Kotaki, Hideyuki; Homma, Takayuki; Kawase, Keigo; Kameshima, Takashi*; Pirozhkov, A. S.; Yogo, Akifumi; et al.
Applied Physics Letters, 95(10), p.101107_1 - 101107_3, 2009/09
Times Cited Count：30 Percentile：73.54(Physics, Applied)Fukuda, Yuji; Faenov, A. Y.; Tampo, Motonobu; Pikuz, T. A.*; Nakamura, Tatsufumi; Kando, Masaki; Hayashi, Yukio; Yogo, Akifumi; Sakaki, Hironao; Kameshima, Takashi; et al.
AIP Conference Proceedings 1153, p.85 - 93, 2009/07
When the target consists of solid-density clusters embedded in the background gas, its irradiation by high intensity laser light renders ion acceleration a truly unique property. We present that the cluster-gas target, which consists of submicron-sized clusters and background gases, irradiated by a few TW laser pulse produces high energy ions upward of the order of 10-20 MeV/n in the forward direction.