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Volume 31, Issue 11
Displaying 1-13 of 13 articles from this issue
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Topical Papers on Science and Technology Created Ultra-Short and Ultra-High Intensity Lasers
Topical Paper
Laser Review
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Hiroyuki DAIDO2003 Volume 31 Issue 11 Pages 696-697
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSDownload PDF (142K) -
Hiroyuki DAIDO2003 Volume 31 Issue 11 Pages 698-706
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSRecently, ultra-high intensity short pulse lasers have been developed quite successfully. They have been applied to the fields such as hard x-ray generation and high energy particle generation. The essence of such laser-produced plasmas is that the lasers can feed their ultra-high energy density into that of the electron motion in matter via the ponderomotive force. Then the electron energy is transferred into the atoms and ions which include excitation and ionization by the laser field and the electron collision. Ion acceleration occurs by the electrostatic potential formed by high energy electron bouncing in the finite size plasma. Subsequently, high flux x-ray with a few tens of MeV energy induces nuclear reactions, which open up the new fields of high energy plasma physics and applications. In this reviewed article, the basic ultra-short and high intensity laser-plasma interaction studies are introduced. These studies lead us to new attractive fields not only the practical applications but also the new aspects of the basic sciences such as control of a highly-nonlinear relativistic plasma.View full abstractDownload PDF (1550K) -
Toshiki TAJIMA2003 Volume 31 Issue 11 Pages 707-710
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSUnder the influence of intense laser electrons begin to behave relativistically. Matter nonlinearly reacts to laser, exhibiting the ‘relativistic nonlinearity’. Because of this property significant novel phenomena manifest themselves. By judiciously utilizing laser and matter, one can realize applications that cannot be accessed by the conventional technology before this. Compact laser acceleration is an example of this relativistic technique. A proper control of the wakefield generated during laser acceleration allows us to focus a counterpropagating another laser into a tiny spot, giving rise to a new method of compressing laser into superstrong intensity in the neighborhood of vacuum breakdown. We survey unique physical research opportunities that this new technique we call relativistic engineering can bring out.View full abstractDownload PDF (2917K) -
Mamiko NISHIUCHI, Hiroyuki DAIDO, Hideaki TAKABE, Koji MATSUKADO2003 Volume 31 Issue 11 Pages 711-720
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSThis review article introduces ultra-high intensity laser driven plasmas for laboratory astrophysics which is currently getting popular in the scientific community. Experiments on radiation hydrodynamics in the laser driven gas-jet target is introduced. The result may contribute to the interpretation of the supernova explosion under the radiative cooling condition. A laser created high-density plasma also nicely contributes to the astrophysics. A femto-second laser whose pulse width is less than 100 fs is instantaneously produces a solid density plasma which is sometimes a strongly coupled and Fermi degenerate plasma. Characterization of such a plasma contributes to the interpretation of physical processes of interior of the stars and planets. The laboratory experiments make physical processes themselves clearer with high precision and reproducibility. Another topic includes ultra-high magnetic fields of more than 10 Mgauss (1000 Tesla) which can be commonly found in stars especially in the neutron stars and the white dwarfs. The quantitative estimation of the field strength in stars is not so easy. The laser driven high magnetic field can also contribute to make diagnostics much more accurate. Finally, the authors emphasize that the ultra-high intensity lasers open new aspects of laser-produced plasmas for laboratory astrophysics.View full abstractDownload PDF (2023K) -
Koji MATSUKADO, Sergei V. BULANOV, Hiroyuki DAIDO2003 Volume 31 Issue 11 Pages 721-729
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSThe hadronic cancer therapy is more attractive than the surgery for localized tumor. However, the hadronic radiotherapy seems not to be easily spread out, because it needs huge capital investments as well as running cost, including an accelerator, gantries and a building for such a radiotherapy system. On the other hand, a laser-plasma ion source will potentially bring us much smaller accelerator system for the hadronic radiotherapy. The laser-plasma ion source is currently developed as an injector for a conventional accelerator or as an advanced accelerator for direct cancer therapy. In this report, we describe present status of radiotherapy system and researches on laser plasma ion sources for radiotherapy.View full abstractDownload PDF (2302K) -
Tomonao HOSOKAI, Alexei ZHIDKOV, Kenichi KINOSHITA, Mitsuru UESAKA2003 Volume 31 Issue 11 Pages 730-736
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSRecently, it is strongly required to develop ultra-short electron beam sources for ultra-fast probe analysis of matter. Among a number of concepts of ultra-short electron bunch production the laser wake-field acceleration (LWFA) provides one of the most promising approaches. In this paper, updated achievements of generation of an ultra-short electron bunch by self-injected LWFA are summarized. We describe latest results of plasma cathode by Univ. of Tokyo, also review the ones by Univ. of Michigan, LBNL (Lawrence Berkeley National Laboratory), and LOA (Laboratoire d’Optique Appliquée).View full abstractDownload PDF (1547K)
Laser Original
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Michiaki MORI, Kiminori KONDO2003 Volume 31 Issue 11 Pages 737-741
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSA commercial base 1.5 TW Ti:Sapphire laser system was improved to be 10 TW one. By improving a design of a chirped plse-amplification of 1.5 TW system, the pulse width was shortened from 100 fs to 40 fs, and the output energy was increased from 150 mJ to 400 mJ. With this system, a high energy electron beam was generated from Ar gasjet target. The maximum energy was more than 4.5 MeV with the electron density of 1.5∼3×1019 cm-3. The effective temperature was estimated to be 0.61 MeV.View full abstractDownload PDF (2338K) -
Yoshio WADA, Atsushi OGATA, Tetsuo KUBOTA2003 Volume 31 Issue 11 Pages 742-746
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSThin (< 10 μm) plastic and metal foils were irradiated by 1 TW, 50 fs laser pulses at an incident angle of π/4. Particle beams were obtained on both sides of the foil with respect to the laser injection. A laser intensity of up to 1017 W cm-2 produced only neutral particle beams on the forward side of the laser propagation with small (∼15°) divergence. When the laser intensity was higher than 1017 W cm-2, a particle beam with larger (> 70°) divergence was observed in addition to that with smaller divergence. The components of the neutrals and ions were contaminants of the foil surface. On the other hand, mainly ions were produced on the backward side, which were components of the target foils. The most energetic particles were protons on both sides, whose energy was about 550 keV.View full abstractDownload PDF (875K) -
Yuji OISHI, Takuya NAYUKI, Takashi FUJII, Yasushi TAKIZAWA, Koshichi N ...2003 Volume 31 Issue 11 Pages 747-751
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSEnergetic protons (∼ 1.2 MeV) were generated by irradiation of ultra-short high-power laser pulses onto a 5 μm thick copper tape target and the dependence of the proton energies on the laser intensity and pulse duration were investigated. The laser intensity was varied between 8.5×1017 W/cm2 and 6.6×1018 W/cm2, and the pulse duration was varied from 55 fs to 400 fs. The maximum proton energy Ep_max and proton temperature were proportional to laser intensity, and they increased with the pulse duration when the laser intensity was kept constant. Thus far, Ep_max has been usually scaled as a function of laser intensity, but Ep_max depends not only on the laser intensity, but also on the pulse duration in an ultra-short pulse regime such as several tens of femto-seconds.View full abstractDownload PDF (682K) -
Eisuke MIURA, Kazuyoshi KOYAMA, Mitsumori TANIMOTO, Susumu KATO, Naoak ...2003 Volume 31 Issue 11 Pages 752-757
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSEmission of a well-collimated energetic electron beam has been observed from a plasma of which electron density is higher than 1020 cm-3 produced by a TW Ti:sapphire laser pulse. The maximum energy of the electrons was 2 MeV, and the beam divergence of the MeV electrons was 6-8°. The generation of the MeV electron beam was always accompanied by the appearance of the transition to the disturbed structure from the narrow and smooth channel in the plasma. This result suggests that the generation of the energetic electron beam may be due to a stochastic acceleration in the disturbed plasma. Discussion based on the stochastic acceleration model taking the phase disturbance of a laser field into account is also presented.View full abstractDownload PDF (929K)
Regular Paper
Laser Original
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Jiasen ZHANG, Shin YOSHIKADO, Tadashi ARUGA2003 Volume 31 Issue 11 Pages 758-761
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSWe propose a compact volume holographic storage system, in which a fiber bundle is used to guide the reference beam. For demonstrating the system, phase-coded multiplexing is implemented by changing the incident direction of the reference beam upon the fiber bundle. Shift multiplexing is also performed by moving the medium. Because no lens or complicated phase modulation system is necessary in the reference arm, the holographic storage system can become more compact. Multiple images are stored in a crystal using the phase coded and shift multiplexing techniques.View full abstractDownload PDF (833K) -
Takayuki SUZUKI, Shinichirou MINEMOTO, Hirofumi SAKAI2003 Volume 31 Issue 11 Pages 762-769
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSWe have developed a closed-loop pulse shaping system with a spatial light modulator, where even a time-dependent polarization pulse can be generated and controlled. An outline of the developed pulse shaping system is described. We apply the developed pulse shaping system to the active control of multiphoton ionization processes in aligned I2 molecules. We perform two kinds of control experiments. First, we show the ability to selectively produce specific multiply-charged molecular ions. Second, we investigate a correlation between a femtosecond time-dependent polarization pulse and the production efficiency of evenly- or oddly-charged molecular ions. We achieve much better controllability of the correlation with a time-dependent polarization pulse than with a pulse having a fixed ellipticity. The results suggest the existence of an unknown tunnel ionization mechanism which is characteristic of an elliptically polarized pulse. Our experiments point to new directions in optimal control studies with molecular systems.View full abstractDownload PDF (1518K)
Technical Note
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Tamotsu EBISAWA, Akihiro YAMAMURA, Masanori JYUMONJI2003 Volume 31 Issue 11 Pages 770-773
Published: 2003
Released on J-STAGE: February 03, 2006
JOURNAL FREE ACCESSA reliable self-starting simmer circuit for use as a Marx-bank driver, in which a stable glow discharge is obtained using the high voltage main power supply instead of an additional simmer power supply, is presented. Highly energetic excitation sources having very short pulse width are needed in powerful dye and excimer lasers. For this reason, multi-stage Marx-bank circuit and LC inversion circuits have been developed. However, these circuits have defects in the interference between the main discharge circuit and the pre-ionization circuit, and an occasional switching failure of the spark gap switch, resulting in an unstable main discharge. The circuit presented seeks to address these issues.View full abstractDownload PDF (459K)
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