Single-shot laser-driven neutron resonance spectroscopy for temperature profiling

Lan, Z.*; Arikawa, Yasunobu*; Mirfayzi, S. R.*; Morace, A.*; Hayakawa, Takehito*; Sato, Hirotaka*; Kamiyama, Takashi*; Wei, T.*; Tatsumi, Yuta*; Koizumi, Mitsuo; et al.

Nature Communications (Internet), 15, p.5365_1 - 5365_7, 2024/07

https://doi.org/10.1038/s41467-024-49142-y

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

https://doi.org/10.1093/ptep/ptu031

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

https://doi.org/10.1093/ptep/ptt023

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

https://doi.org/10.1585/pfr.7.2404010

Experimental evidence of nonthermal acceleration of relativistic electrons by an intensive laser pulse

Kuramitsu, Yasuhiro*; Nakanii, Nobuhiko*; Kondo, Kiminori; Sakawa, Yoichi*; Mori, Yoshitaka*; Miura, Eisuke*; Tsuji, Kazuki*; Kimura, Kazuya*; Fukumochi, Shuji*; Kashihara, Mamoru*; et al.

Physical Review E, 83(2), p.026401_1 - 026401_6, 2011/02

https://doi.org/10.1103/PhysRevE.83.026401

An energy distribution function of energetic particles in the universe or cosmic rays is well represented by a power-law spectrum, therefore, nonthermal acceleration is essential to understand the origin of cosmic rays. A possible candidate for the origin of cosmic rays is wakefield acceleration at relativistic astrophysical perpendicular shocks. Substituting an intensive laser pulse for the large amplitude light waves, we performed a model experiment of the shock environments in a laboratory plasma.

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

https://doi.org/10.1088/0741-3335/52/12/124047

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.

Tomography of an ultrafast laser driven proton source

Ter-Avetisyan, S.*; Schnrer, M.*; Nickles, P. V.*; Sandner, W.*; Borghesi, M.*; Nakamura, Tatsufumi; Mima, Kunioki*

Physics of Plasmas, 17(6), p.063101_1 - 063101_6, 2010/06

https://doi.org/10.1063/1.3428740

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.

Guiding and confining fast electrons by transient electric and magnetic fields with a plasma inverse cone

Lei, A. L.*; Cao, L. H.*; Yang, X. Q.*; Tanaka, Kazuo*; Kodama, Ryosuke*; He, X. T.*; Mima, Kunioki*; Nakamura, Tatsufumi; Norimatsu, Takayoshi*; Yu, W.*; et al.

Physics of Plasmas, 16(2), p.020702_1 - 020702_4, 2009/02

https://doi.org/10.1063/1.3075928

The fast electron propagation in an inverse cone target is investigated computationally and experimentally. Two-dimensional particle-in-cell simulation shows that fast electrons with substantial numbers are generated at the outer tip of an inverse cone target irradiated by a short intense laser pulse. These electrons are guided and confined to propagate along the inverse cone wall, forming a large surface current. The experiment qualitatively verifies the guiding and confinement of the strong electron current in the wall surface. The large surface current and induced strong field s are of importance for fast ignition related research.

Time-resolved fluorescence spectrum of wide-gap semiconductors excited by 13.9 nm X-ray laser

Tanaka, Momoko; Furukawa, Yusuke*; Nakazato, Tomoharu*; Tatsumi, Toshihiro*; Murakami, Hidetoshi*; Shimizu, Toshihiko*; Sarukura, Nobuhiko*; Nishikino, Masaharu; Kawachi, Tetsuya; Kagamitani, Yuji*; et al.

X-Ray Lasers 2008; Springer Proceedings in Physics, Vol.130, p.501 - 505, 2009/00

https://doi.org/10.1007/978-1-4020-9924-3_60

We measured the time-resolved fluorescence spectra of ZnO and GaN single crystals excited by an X-ray laser operating at 13.9 nm and evaluated their scintillation properties for EUV excitation as compared with UV excitation case. For ZnO, a clear fluorescence peak of excitonic origin was observed at around 380 nm and the decay lifetime of less than 3 ns is found to be almost similar to the UV excitation case. The fluorescence at 380 nm is ideal for scintillator device design in the EUV and further applications. For GaN, the lifetimes are much longer than ZnO and the temporal profile of the EUV-excited fluorescence differs with the UV excitation case. As such, the EUV scintillation properties of ZnO is said to be more favorable than GaN. Finally, it is also demonstrated that an X-ray laser is an excellent tool for spectroscopic characterization of materials intended for next-generation lithography applications.

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

https://doi.org/10.1063/1.2983150

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.