Akagi, Hiroshi*; Kumada, Takayuki; Otobe, Tomohito*; Itakura, Ryuji*; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
Applied Physics B, 124(1), p.14_1 - 14_8, 2018/01
We propose and numerically simulate a method of laser isotope separation based on field-free alignment of isotopologues, utilizing an intense switched nanosecond (ns) laser field which is slowly turned on and rapidly turned off at the peak with the falling time of 200 fs. The femtosecond (fs) laser induced alignment of molecules including a heavy atom is severely disturbed by ionization because of their small ionization potential. Our simulations for Br and Br isotopologues demonstrate that the switched ns laser field can make isotopologues well-aligned with the reduced ionization probability at the laser intensity which is an order-of-magnitude lower than a typical intensity for field-free alignment induced by a fs laser field.
Inogamov, N. A.*; Zhakhovsky, V. V.*; Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Ishino, Masahiko; Agranat, M. B.*; Ashitkov, S. I.*; Faenov, A. Y.*; Khokhlov, V. A.*; et al.
Applied Physics B, 119(3), p.413 - 419, 2015/06
Akagi, Hiroshi; Kasajima, Tatsuya; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*
Applied Physics B, 109(1), p.75 - 80, 2012/10
We demonstrate a laser nitrogen isotope separation, which is based on field-free alignment and angular dependent ionization of N and N isotopomers. A linearly-polarized short laser pulse (795 nm, 60 fs) creates rotational wave packets in the isotopomers, which periodically revive with different revival times as a result of different moments of inertia. Another linearly-polarized short laser pulse (795 nm, 60 fs) ionizes one of the isotopomers selectively as a result of their different angular distributions. In the present experiments, the ion yield ratio [= (N)/(N)] can be changed in the range from 0.85 to 1.22, depending on the time delay between the two laser pulses.
Suzuki, Masayuki*; Kiriyama, Hiromitsu; Daito, Izuru; Ochi, Yoshihiro; Okada, Hajime; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; Maeda, Junya*; Matsuoka, Shinichi*; et al.
Applied Physics B, 105(2), p.181 - 184, 2011/11
We have demonstrated an OPCPA/Yb:YAG ceramic thin disk hybrid laser system having hundred mJ level pulse energy sub-picosecond pulse duration with high temporal contrast. At an input energy of 3.8 mJ from an OPCPA preamplifier an output energy of 130 mJ was obtained from Yb:YAG ceramic thin disk amplifier. A recompressed pulse duration of 450 fs with a contrast level of less than 7.210 was obtained. The contrast level is the highest value achieved in Yb:YAG chirped pulse amplification (CPA) laser system with hundred mJ level.
Hashimoto, Masashi; Oba, Hironori; Yokoyama, Atsushi
Applied Physics B, 104(4), p.969 - 974, 2011/09
Oxygen isotope separation has been examined by utilizing the two-frequency infrared multiphoton dissociation (IRMPD) of 2,3-dihydropyran (DHP). The two-frequency IRMPD reduces remarkably the required laser fluence. For example, dissociation probability of DHP containing O (D(O)) and enrichment factor (S) were obtained to be 1.610 /pulse and 316 respectively by the simultaneous irradiation with 1052.2 cm photons at 0.45 J/cm and 1031.5 cm photons at 1.06 J/cm. These are comparable with D(O) = 2.210 /pulse and S = 391 obtained by the single-frequency irradiation of 1033.5 cm photons at 2.2 J/cm. Therefore, the production rate of an O enriched dissociation product has been increased to four times or more, compared with the single-frequency IRMPD, and this two-frequency method would promise a practical large scale separation.
Yazawa, Hiroki*; Shioyama, Tadamasa*; Hashimoto, Hiroshi*; Kannari, Fumihiko*; Itakura, Ryuji; Yamanouchi, Kaoru*
Applied Physics B, 98(2-3), p.275 - 282, 2010/02
We experimentally investigate the dynamics of vibrational wave packets on the light-dressed-potential energy surface (LD-PES) of CHOH using a pump-and-probe pulse excitation scheme. The probability of non-adiabatic transition at 800 nm from the singly ionized ground state to the repulsive excited state leading to C-O bond breaking is enhanced when a probe laser pulse is delayed by around 180 fs. At this pulse delay, on the other hand, C-C bond breaking is significantly suppressed. Therefore, the deformation of LDPES is considered to change the direction of the wave packet traveling originally along the C-C stretching into the direction along the C-O stretching. This non-adiabatic transition leading to the redirection of the dissociating wave packet is found to occur more efficiently at the probe laser wavelengths at 400 nm than at 800 nm. The critical pulse delay is still around 180 fs even at 400 nm.
Suzuki, Masayuki; Kiriyama, Hiromitsu; Daito, Izuru; Okada, Hajime; Nakai, Yoshiki; Orimo, Satoshi; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; Maeda, Junya*; et al.
Applied Physics B, 97(2), p.379 - 382, 2009/10
We report the highest energy broadband laser pulses at a center wavelength of 1030 nm based on optical parametric chirped-pulse amplification (OPCPA). We have demonstrated amplification of 1030 nm femtosecond laser pulses from a broadband Yb oscillator to over 6.5 mJ with a total gain of greater than 10 achieved in a single pass through only 56 mm of gain material at a 10 Hz repetition rate. The amplified spectral bandwidth of 10.8 nm affords recompression to a 230 fs pulse duration following amplification. As an alternative to the regenerative amplifier (RA) this system is one of the more promising candidates for realizing compact, high intensity, direct diode pumped, high repetition rate femtosecond Yb:YAG chirped-pulse amplification (CPA) in laser systems.
Akagi, Hiroshi; Oba, Hironori; Yokoyama, Keiichi; Yokoyama, Atsushi; Egashira, Kazuhiro*; Fujimura, Yo*
Applied Physics B, 95(1), p.17 - 21, 2009/04
We have proposed a laser isotope separation method, utilizing rotational coherence of a simple molecule. In the scheme, photoexcited molecules are isotopically separated by difference of rotational period between them. To illustrate this method, two-pulse photodissociation of mixed Br/Br isotopes has been investigated theoretically. The photodissociation probabilities of Br and Br have been calculated as a function of time delay between the photoexcitation and dissociation laser pulses. We have demonstrated that isotope enrichment factor of Br relative to Br can be changed from 0.34 to 1.8, by simply changing the time delay only by 0.2 ns. Additionally, we have shown that this method is effective for heavy isotopes, based on mass dependence of the isotope enrichment factor.
Sagisaka, Akito; Daido, Hiroyuki; Nashima, Shigeki*; Orimo, Satoshi; Ogura, Koichi; Mori, Michiaki; Yogo, Akifumi; Ma, J.-L.; Daito, Izuru; Pirozhkov, A. S.; et al.
Applied Physics B, 90(3-4), p.373 - 377, 2008/03
High-intensity laser and thin-foil interactions produce high energy ions, electrons, hard X-ray, and terahertz radiation. The simultaneous generation of the protons and terahertz radiation will provide us unique applications. In this study we use a Ti:sapphire laser system (JLITE-X) at JAEA for simultaneous generation of the protons and terahertz radiation. The laser beam is focused by an off-axis parabolic mirror at the Ti target surface. The estimated peak intensity is 210W/cm. The simultaneous generation of the protons and terahertz radiation are observed by reducing the ASE duration.
Sagisaka, Akito; Pirozhkov, A. S.; Daido, Hiroyuki; Fukumi, Atsushi*; Li, Z.*; Ogura, Koichi; Yogo, Akifumi; Oishi, Yuji*; Nayuki, Takuya*; Fujii, Takashi*; et al.
Applied Physics B, 84(3), p.415 - 419, 2006/09
no abstracts in English
Yogo, Akifumi; Nishiuchi, Mamiko; Fukumi, Atsushi*; Li, Z.*; Ogura, Koichi; Sagisaka, Akito; Orimo, Satoshi; Kado, Masataka; Hayashi, Yukio; Mori, Michiaki; et al.
Applied Physics B, 83(4), p.487 - 489, 2006/06
We present experimental results on protons accelerated up to 950 keV from a 3-m thick tantalum foil with a 133-nm thick polystyrene layer on its rear surface, irradiated with a laser pulse having the duration of 70 fs and the intensity of W/cm. The energy distribution of fast protons was measured simultaneously with that of the hot-electrons from the rear surface. The proton yield from the polystyrene-coated target is about 10 times as high as that from the uncoated metal target. This enhancement of the proton yield is roughly proportional to the increase of hydrogen atoms given by the 133-nm thick polystyrene layer, assuming a contaminant layer of 10-nm thickness is on the metal surface without coating. This result shows that the polystyrene layer contributes to the yield enhancement.
Wang, H.*; Oba, Hironori; Saeki, Morihisa; Miyabe, Masabumi; Shibata, Takemasa; Miyatake, Hiroari*; Iimura, Hideki
Applied Physics B, 81(8), p.1127 - 1133, 2005/12
Laser-induced fluorescence spectroscopy has been employed to characterize the plume produced in nanosecond laser ablation of metallic neodymium. The kinetic-energy distributions of the neutral and ionized atoms in the plume under both vacuum and gas environments have been investigated. The population distribution of metastable levels in the ablated atoms was also derived. The results show some metastable states are more heavily populated than predicted by a Boltzman-type distribution. These investigations provide preliminary data for the design of a new type of resonance photo-ionization laser ion source as well as for hign-resolution laser spectroscopy of refractory elements.
Yokoyama, Atsushi; Oba, Hironori; Hashimoto, Masashi; Katsumata, Keiichi; Akagi, Hiroshi; Ishii, Takeshi*; Oya, Akio*; Arai, Shigeyoshi*
Applied Physics B, 79(7), p.883 - 889, 2004/11
Silicon isotope separation has been done utilizing the Infrared Multiphoton Dissociation of SiF irradiated with two-frequency CO laser lights. The two-frequency excitation method improved the separation efficiency with keeping the high enrichment factors. For example, SiF with the Si fraction of 99.4 % was obtained at 40.0 % dissociation of SiF after the simultaneous irradiation of 100 pulses with 966.23 cm photons (0.089 J/cm) and 954.55 cm photons (0.92 J/cm), while 1000 pulses were needed to obtain 99.0 % of Si at 27.2 % dissociation in the case of single frequency irradiation at 954.55 cm (0.92 J/cm). The single-step enrichment factors of Si and Si increased with increasing SiF pressure. The reason for this enhancement has been discussed in terms of the rotational and vibrational relaxations by collisions with ambient gases.
Nagashima, Keisuke; Tanaka, Momoko; Nishikino, Masaharu; Kishimoto, Maki; Kado, Masataka; Kawachi, Tetsuya; Hasegawa, Noboru; Ochi, Yoshihiro; Sukegawa, Kota*; Tai, R.; et al.
Applied Physics B, 78(7), p.927 - 932, 2004/05
We have succeeded in developing a laser-pumped X-ray laser with full spatial coherence at 13.9 nm. A highly directed X-ray laser beam with the divergence of 0.2 mrad was generated from the double target experiment, where a seeding light from the first laser medium was amplified in the second medium. The observed divergence is close to the diffraction limit value within a factor of two. The seeding light was amplified in the second medium without refraction influence and the gain coefficient was about 8 cm-1. From the measurement of visibility, it was found that the spatial coherent length is longer than the beam diameter. As an application of this coherent X-ray laser, we observed a surface microstructure of ferroelectric material, BaTiO and clarified a change of the microstructure near the Curie temperature.
Sagisaka, Akito; Daido, Hiroyuki; Ogura, Koichi; Orimo, Satoshi; Hayashi, Yukio; Nishiuchi, Mamiko; Mori, Michiaki; Matsukado, Koji*; Fukumi, Atsushi*; Li, Z.*; et al.
Applied Physics B, 78(7-8), p.919 - 922, 2004/05
no abstracts in English
Aoyama, Makoto*; Sagisaka, Akito; Matsuoka, Shinichi*; Akahane, Yutaka; Nakano, Fumihiko*; Yamakawa, Koichi
Applied Physics B, 70(Suppl.), p.S149 - S153, 2000/06
no abstracts in English
Sagisaka, Akito; *; Kondo, Kiminori*; Suzuki, Hajime*; Nagashima, Keisuke; Nagashima, Akira; Kawachi, Tetsuya; Kato, Yoshiaki; Takuma, Hiroshi
Applied Physics B, 70(4), p.549 - 554, 2000/04
no abstracts in English
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Applied Physics B, 38(2), p.99 - 105, 1985/00
no abstracts in English