Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 49

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

New measurement of the $$^{8}$$Li($$alpha$$,n)$$^{11}$$B reaction in a lower-energy region below the Coulomb barrier

Das, S. K.*; Fukuda, Tomokazu*; Mizoi, Yutaka*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Jeong, S. C.*; Ikezoe, Hiroshi*; Matsuda, Makoto; et al.

Physical Review C, 95(5), p.055805_1 - 055805_4, 2017/05

 Times Cited Count:0 Percentile:100(Physics, Nuclear)

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Journal Articles

A New measurement of the astrophysical $$^8$$Li(d,t)$$^7$$Li reaction

Hashimoto, Takashi; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Jeong, S.-C.*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Nomura, Toru*; et al.

Physics Letters B, 674(4-5), p.276 - 280, 2009/04

 Times Cited Count:6 Percentile:53.37(Astronomy & Astrophysics)

The excitation function of the $$^8$$Li(d,t)$$^7$$Li reaction was directly measured using $$^8$$Li beams at E$$_{mathrm{cm}}$$ = 0.3, 0.4, 0.5, 0.7, 0.8, 1.0, 1.1, and 1.2 MeV with CD$$_2$$ targets. The beam energies covered the Gamow peaks for 1$$sim$$3$$times$$10$$^9$$ K. Large cross sections were observed at around E$$_{mathrm{cm}}$$ = 0.8 MeV, implying a resonance state located at 22.4 MeV in $$^{10}$$Be. The present astrophysical reaction rate is higher in one order magnitude than the presently adopted rate at around 1$$times$$10$$^9$$ K.

Journal Articles

Spectroscopic characterization of ultrashort laser driven targets incorporating both Boltzmann and particle-in-cell models

Sherrill, M. E.*; Abdallah, J.*; Csanak, G.*; Dodd, E. S.*; Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki*; Yamakawa, Koichi; et al.

High-Power Laser Ablation VII (Proceedings of SPIE Vol.7005), p.70051R_1 - 70051R_11, 2008/06

Journal Articles

Progress in R&D efforts on the energy recovery linac in Japan

Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.

Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06

Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.

Journal Articles

Ultrarelativistic electron generation during the intense, ultrashort laser pulse interaction with clusters

Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Hayashi, Yukio; Homma, Takayuki; Inoue, Norihiro*; Kando, Masaki; Kanazawa, Shuhei; Kiriyama, Hiromitsu; Kondo, Shuji; et al.

Physics Letters A, 363(2-3), p.130 - 135, 2007/02

Collimated relativistic electrons up to 58 MeV with an electron charge of 2.1 nC were generated by the interaction of intense laser pulses with the Ar cluster target at the laser intensity of 3.5$$times$$10$$^{19}$$W/cm$$^{2}$$. The resulting spectrum does not fit a Maxwellian distribution, but is well described by a two-temperature Maxwellian, which indicates two mechanisms of the electron acceleration. Two dimensional particle-in-cell simulations demonstrate an important role of clusters. The higher energy electrons are injected when they are expelled from the clusters by the laser pulse field. They then gain their energy during the direct acceleration by the laser pulse, whose phase velocity in the underdense plasma is larger than speed of light in vacuum. The lower energy electrons, which are injected during the plasma wave breaking, are accelerated by the wakefield.

Journal Articles

A New measurement of the astrophysical $$^8$$Li($$alpha$$, n)$$^{11}$$B reaction

Ishiyama, Hironobu*; Hashimoto, Takashi; Ishikawa, Tomoko*; Watanabe, Yutaka*; Das, S. K.*; Miyatake, Hiroari; Mizoi, Yutaka*; Fukuda, Tomokazu*; Tanaka, Masahiko*; Fuchi, Yoshihide*; et al.

Physics Letters B, 640(3), p.82 - 85, 2006/09

 Times Cited Count:31 Percentile:13.74(Astronomy & Astrophysics)

The excitation function of the $$^{8}$$Li($$alpha$$,n)$$^{11}$$B reaction was measured while identifying the final state event by event in the region of E$$_{rm{cm}}$$ = 0.7 - 2.6 MeV using a highly efficient detector system and a low-energy $$^8$$Li beam. The results are much improved both in statistics and precisions, and show smaller cross sections than those of previous measurements by a factor of more than 2 in the low-energy region of E$$_{rm{cm}}le$$ 1.5 MeV. A resonance-like structure is found at around E$$_{rm{cm}}$$ = 0.85 MeV.

Journal Articles

A New measurement of the $$^8$$Li($$alpha$$,n)$$^{11}$$B reaction for astrophysical interest

Das, S. K.*; Fukuda, Tomokazu*; Mizoi, Yutaka*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Jeong, S.-C.*; et al.

AIP Conference Proceedings 847, p.374 - 376, 2006/07

no abstracts in English

Journal Articles

Spectroscopic characterization of an ultrashort-pulse-laser-driven Ar cluster target incorporating both Boltzmann and particle-in-cell models

Sherrill, M. E.*; Abdallah, J. Jr.*; Csanak, G.*; Dodd, E. S.*; Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki*; Yamakawa, Koichi; et al.

Physical Review E, 73(6), p.066404_1 - 066404_6, 2006/06

 Times Cited Count:29 Percentile:20.63(Physics, Fluids & Plasmas)

A model that solves simultaneously both the electron and atomic kinetics was used to generate synthetic He$$_alpha$$ X-ray spectra to characterize a high intensity ultrashort laser driven Ar cluster target experiment. In particular, level populations were obtained from a detailed collisional-radiative model where collisional rates were computed from a time varying electron distribution function obtained from the solution of the zero dimensional Boltzmann equation. In addition, aparticle-in-cell simulation was used to model the laser interaction with the cluster target and provided the initial electron energy distribution function (EEDF) for the Boltzmann solver. This study suggests that the high density plasma contribution to the time-integrated He$$_alpha$$ spectrum was in a highly non-equilibrium state in both the EEDF and the ion level populations and provides a prediction of 5.7 ps for the average cluster integrity time for this high density state.

Journal Articles

Coupled electron and atomic kinetics through the solution of the Boltzmann equation for generating time-dependent X-ray spectra

Sherrill, M. E.*; Abdallah, J. Jr.*; Csanak, G.*; Kilcrease, D. P.*; Dodd, E. S.*; Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki; et al.

Journal of Quantitative Spectroscopy & Radiative Transfer, 99(1-3), p.584 - 594, 2006/05

 Times Cited Count:2 Percentile:85.85(Optics)

In this work, we present a model that solves self-consistently the electron and atomic kinetics to characterize highly non-equilibrium plasmas, in particular for those systems where both the electron distribution function is far from Maxwellian and the evolution of the ion level populations are dominated by time dependent atomic kinetics. In this model, level populations are obtained from a detailed collisional-radiative model where collision rates are computed from a time varying electron distribution function obtained from the solution of the zero-dimensional Boltzmann equation. The Boltzmann collision term includes the effects of electron-electron collisions, electron collisional ionization, excitation and de-excitation. An application for He$$_alpha$$ spectra from a short pulse laser irradiated argon cluster target will be shown to illustrate the results of our model.

Journal Articles

Production of a low-energy radioactive nuclear beam with high purity using JAERI-RMS

Ishiyama, Hironobu*; Ishikawa, Tomoko*; Hashimoto, Takashi; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Tanaka, Masahiko*; Fuchi, Yoshihide*; Yoshikawa, Nobuharu*; et al.

Nuclear Instruments and Methods in Physics Research A, 560(2), p.366 - 372, 2006/05

 Times Cited Count:7 Percentile:50.31(Instruments & Instrumentation)

Thanks to the nature of inverse transfer-reactions, low-energy radioactive nuclear beams in light neutron-rich region were produced. The mass-separation and velocity-separation of the JAERI recoil mass-separator help to form high purity beams. The beams of $$^8$$Li, $$^{12}$$B, and $$^{16}$$N-RNBs are utilized to the experiments, so far, with those beam intensities and purities of 1.4$$times$$10$$^4$$ pps and 99$$%$$, 7.8$$times$$10$$^3$$ pps and 98$$%$$, and 4.7$$times$$10$$^3$$ pps and 98.5$$%$$, respectively.

Journal Articles

Characterization of wave-front corrected 100 TW, 10 Hz laser pulses with peak intensities greater than 10$$^{20}$$ W/cm$$^{2}$$

Akahane, Yutaka; Ma, J.-L.; Fukuda, Yuji; Aoyama, Makoto; Kiriyama, Hiromitsu; Sheldakova, J. V.*; Kudryashov, A. V.*; Yamakawa, Koichi

Review of Scientific Instruments, 77(2), p.023102_1 - 023102_7, 2006/02

 Times Cited Count:40 Percentile:14.08(Instruments & Instrumentation)

An improvement of laser-focused peak intensity has been achieved in a JAERI 100-TW Ti:sapphire chirped-pulse amplifier chain with a feedback controlled adaptive optics system operating at a 10 Hz repetition rate. The Strehl ratio was enhanced to 0.8 by means of a Bimorph deformable mirror with a Shack-Hartmann wavefront sensor. Measurements of optical parameters of the laser pulse and an experimental tunneling ionization yield of helium have practically confirmed focusing to ultra-relativistic intensities of over 10$$^{20}$$ W/cm$$^{2}$$ within 16 % accuracy.

Journal Articles

Gated multiple-sampling and tracking proportional chamber; New detector system for nuclear astrophysical study with radioactive nuclear beams

Hashimoto, Takashi; Ishiyama, Hironobu*; Ishikawa, Tomoko*; Kawamura, Takashi*; Nakai, Koji*; Watanabe, Yutaka*; Miyatake, Hiroari; Tanaka, Masahiko*; Fuchi, Yoshihide*; Yoshikawa, Nobuharu*; et al.

Nuclear Instruments and Methods in Physics Research A, 556(1), p.339 - 349, 2006/01

 Times Cited Count:30 Percentile:10.25(Instruments & Instrumentation)

A new type of three dimensional tracking and proportional gas counter has been developed. Adopting a gating-grid system, performance of the detector becomes stable under the injection rate of charged particles less than 4$$times$$10$$^4$$ pps. It is a useful detection system for astrophysical experiments using radioactive nuclear beams, since the efficiency is so high as 100 %.

Journal Articles

Generation and evaluation of a 10$$^{20}$$ W/cm$$^{2}$$ intensity by focusing wavefront corrected 100 TW, 10 Hz laser pulses

Akahane, Yutaka; Ma, J.; Fukuda, Yuji; Aoyama, Makoto; Kiriyama, Hiromitsu; Inoue, Norihiro*; Tsuji, Koichi*; Nakai, Yoshiki*; Yamamoto, Yoichi*; Sheldakova, J. V.*; et al.

Japanese Journal of Applied Physics, Part 1, 44(8), p.6087 - 6089, 2005/08

 Times Cited Count:1 Percentile:94.87(Physics, Applied)

An improvement of laser-focused peak intensity has been achieved in a JAERI 100 TW Ti:sapphire chirped-pulse amplifier chain with a feedback-controlled adaptive optics system. Measurements of optical parameters of the laser pulse and an experimental tunneling ionization ratio of a rare gas atom with laser energy scaling have practically confirmed an ultrarelativistic intensity of over 10$$^{20}$$ W/cm$$^{2}$$ operating at a 10 Hz repetition rate.

Journal Articles

Measurement of $$2l-nl$$' X-ray transitions from $$approx$$1 $$mu$$m Kr clusters irradiated by high-intensity femtosecond laser pulses

Hansen, S. B.*; Fournier, K. B.*; Faenov, A. Y.*; Magunov, A. I.*; Pikuz, T. A.*; Skobelev, I. Y.*; Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; et al.

Physical Review E, 71(1), p.016408_1 - 016408_9, 2005/01

 Times Cited Count:15 Percentile:40.68(Physics, Fluids & Plasmas)

X-ray line emission from $$2l-nl$$' transitions in Ne-like Kr and nearby ions has been observed from $$approx$$ 1 $$mu$$m Kr clusters irradiated by fs-scale laser pulses at the JAERI facility in Kyoto, Japan. The dependence of X-ray spectral features and intensity on the incident laser intensity is rather weak, indicating that the 1-2 ps cluster lifetimes limit the number of ions beyond Ne-like Kr that can be produced by collisional ionization. A collisional-radiative model based on the relativistic multiconfigured FAC code has been constructed and used to determine that the cluster plasma has electron densities near 10$$^{22}$$ cm$$^{-3}$$, temperature of a few hundred eV and hot electron fraction of a few percent.

Journal Articles

Relativistic laser plasma from micron-sized argon clusters as a debris-free X-ray source for pulse X-ray diffraction

Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki; Nakai, Yoshiki*; Tsuji, Koichi*; Yamakawa, Koichi; Hironaka, Yoichiro*; Kishimura, Hiroaki*; et al.

Applied Physics Letters, 85(21), p.5099 - 5101, 2004/11

 Times Cited Count:10 Percentile:57.67(Physics, Applied)

We have demonstrated diffraction from Si(111) crystal using X-rays from highly ionized Ar ions produced by laser irradiation with an intensity of 6$$times$$10$$^{18}$$ W/cm$$^{2}$$ and a pulse duration of 30 fs acting upon micron-sized Ar clusters. The measured total photon flux and line width in the He$$_{alpha1}$$ line (3.14 keV) were 4$$times$$10$$^{7}$$ photons/shot/4$$pi$$sr and 3.7 eV (FWHM), respectively, which is sufficient to utilize as a debris-free light source for time-resolved X-ray diffraction studies.

Journal Articles

Generation of X-rays and energetic ions from superintense laser irradiation of micron-sized Ar clusters

Fukuda, Yuji; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki; Kishimoto, Yasuaki; Yamakawa, Koichi; Faenov, A. Y.*; Magunov, A. I.*; Pikuz, T. A.*; et al.

Laser and Particle Beams, 22(3), p.215 - 220, 2004/07

High resolution K-shell spectra of a plasma created by superintense laser irradiation of micron-sized Ar clusters have been measured with an intensity above 10$$^{19}$$ W/cm$$^2$$ and a pulse duration of 30 fs. The total photon flux of 2$$times$$10$$^8$$ photons/pulse was achieved for He$$_{alpha1}$$ resonant line of Ar ($$lambda$$=3.9491 AA , 3.14 keV). In parallel with X-ray measurements, energy distributions of emitted ions have been measured. The multiply-charged ions with kinetic energies up to 800 keV were observed. It is found that hot electrons produced by high contrast laser pulses allow the isochoric heating of clusters and shift the ion balance towards the higher charge states, which enhances both the X-ray line yield of the He-like argon ion and the ion kinetic energy.

Journal Articles

Microdroplet evolution induced by a laser pulse

Smirnov, M. B.*; Skobelev, I. Y.*; Magunov, A. I.*; Faenov, A. Y.*; Pikuz, T. A.*; Fukuda, Yuji; Yamakawa, Koichi; Akahane, Yutaka; Aoyama, Makoto; Inoue, Norihiro*; et al.

Journal of Experimental and Theoretical Physics, 98(6), p.1123 - 1132, 2004/06

Interaction between high-power ultrashort laser pulse and giant clusters (microdroplets) consisting of 10$$^9$$ to 10$$^{10}$$ atoms is considered. The microdroplet size is comparable to the laser wavelength. A model of the evolution of a microdroplet plasma induced by a high-power laser pulse is developed, and the processes taking place after interaction with the pulse are analyzed. It is shown theoretically that the plasma is superheated: its temperature is approximately equal to the ionization potential of an ion having a typical charge. The microdroplet plasma parameters are independent of the pulse shape and duration. The theoretical conclusions are supported by experimental studies of X-ray spectra conducted at JAERI, where a 100-terawatt Ti-sapphire lasersystem was used to irradiate krypton and xenon microdroplets by laser pulses with pulse widths of 30 to 500 fs and intensities of 6$$times$$10$$^{16}$$ to 2$$times$$10$$^{19}$$ W/cm$$^{2}$$.

Journal Articles

Optimal control of ultrafast selection

Yokoyama, Keiichi; Teranishi, Yoshiaki; Toya, Yukio; Shirai, Toshizo; Fukuda, Yuji; Aoyama, Makoto; Akahane, Yutaka; Inoue, Norihiro*; Ueda, Hideki; Yamakawa, Koichi; et al.

Journal of Chemical Physics, 120(20), p.9446 - 9449, 2004/05

 Times Cited Count:5 Percentile:83.23(Chemistry, Physical)

Optimal laser control for ultrafast selection of closely-lying excited states, whose energy separation is smaller than the laser bandwidth, is reported on the two-photon transition of atomic cesium; Cs(6S $$rightarrow$$ 7D$$_{J}$$, J = 5/2 and 3/2). Selective excitation was carried out by pulse shaping of ultrashort laser pulses which were adaptively modulated in a closed-loop learning system handling eight parameters representing the electric field. Two-color fluorescence from the respective excited states was monitored to measure the selectivity. The fitness used in the learning algorithm was evaluated from the ratio of the fluorescence yield. After fifty generations, a pair of nearly transform-limitted pulses were obtained as an optimal pulse shape, proving the effectiveness of "Ramsey fringes" mechanism. The contrast of the selection ratio was improved by $$sim$$ 30 % from the simple "Ramsey fringes" experiment.

Journal Articles

Many-electron dynamics of a Xe atom in strong and superstrong laser fields

Yamakawa, Koichi; Akahane, Yutaka; Fukuda, Yuji; Aoyama, Makoto; Inoue, Norihiro*; Ueda, Hideki; Utsumi, Takayuki*

Physical Review Letters, 92(12), p.123001_1 - 123001_4, 2004/03

 Times Cited Count:62 Percentile:11.77(Physics, Multidisciplinary)

We report on detailed investigations of ionization dynamics of a Xe atom exposed to intense 800-nm pulses of 20-fs duration in the extensive intensity range from 10$$^{13}$$ to 10$$^{18}$$ W/cm$$^{2}$$. Ion yields of Xe$$^{+}$$ to Xe$$^{20+}$$ were observed as a function of laser intensity and compared with the results from a single active electron based Ammosov-Delone-Krainov model. Unexpected ionization probabilities for lower charge states and also no interplay between the inner- and outer-shells by screening are inferred. Suppression of nonsequential ionization towards higher intensity and few optical cycle regimes is also proved.

49 (Records 1-20 displayed on this page)