Miyabe, Masabumi; Satou, Yukihiko; Wakaida, Ikuo; Terabayashi, Ryohei*; Sonnenschein, V.*; Tomita, Hideki*; Zhao, Y.*; Sakamoto, Tetsuo*
Journal of Physics B; Atomic, Molecular and Optical Physics, 54(14), p.145003_1 - 145003_8, 2021/07
Two-color two-step photoionization optogalvanic spectroscopy was performed using high-repetition-rate titanium sapphire lasers and a uranium hollow cathode lamp to find the two-step resonance ionization schemes of uranium. Many ionization transitions were observed by exciting uranium atoms in a ground state into five, even parity, excited levels with the first-step laser and by scanning the second-step laser wavelengths. By blocking the first-step laser, single-color, two-photon ionization transitions were also identified. From these results, we have found more than 50 odd-parity autoionizing levels of uranium in the energy, ranging from the ionization potential (49958.4 cm) to 51150 cm. The determined energy levels are within 1 cm of previously reported values.
Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*
Journal of Physics B; Atomic, Molecular and Optical Physics, 2 Pages, 2016/01
Collaboration of researchers from Japan Atomic Energy Agency and EUROfusion Consortium (Dutch Institute For Fundamental Energy Research, Max-Planck-Institut fr Plasmaphysik and so on) successfully led to determination of tungsten ion density in high temperature plasmas in Joint European Torus (JET) with an upgraded X-ray spectrometer. The researchers used the FAC code and successfully identified , and spectral lines. The line identification was confirmed experimentally by Mo injection to the plasma. From the measured absolute intensity of these spectral lines, tungsten and molybdenum ion densities in the plasma core were determined.
Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*; Reinke, M.*; Lawson, K.*; Coffey, I.*; Ptterich, T.*; Brezinsek, S.*; Lipschultz, B.*; Matthews, G. F.*; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 48(14), p.144023_1 - 144023_11, 2015/07
The and 3p-4d inner shell excitation lines in addition to 2p-3s lines have been identified from the spectrum taken by an upgraded high-resolution X-ray spectrometer. It is found from analysis of the absolute intensities of the and lines that W and Mo concentrations are in the range of and , respectively, with a ratio of 5% for ELMy H-mode plasmas with a plasma current of 2.0- 2.5 MA, a toroidal magnetic field of 2.7 T and a neutral beam injection power of 14-18 MW. For the purpose of checking self-consistency, it is confirmed that the W concentration determined from the line is in agreement with that from the line within 20% and that the plasma effective charge determined from the continuum of the first order reflection spectrum is also in agreement with that from the second order within 50%. Further, the determined plasma effective charge is in agreement with that determined from a visible spectroscopy, confirming that the sensitivity of the X-ray spectrometer is valid and that probably the W and the Mo concentrations are also valid.
Harries, J.; Iwayama, Hiroshi*; Nagasono, Mitsuru*; Togashi, Tadashi*; Yabashi, Makina*; Kuma, Susumu*; Nakajima, Kyo*; Miyamoto, Yuki*; Ohae, Chiaki*; Sasao, Noboru*; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 48(10), p.105002_1 - 105002_9, 2015/05
Itakura, Ryuji; Fushitani, Mizuho*; Hishikawa, Akiyoshi*; Sako, Tokuei*
Journal of Physics B; Atomic, Molecular and Optical Physics, 47(19), p.195602_1 - 195602_9, 2014/10
Ultrafast multichannel single-photon ionization of Ar is investigated theoretically by a model calculation incorporating correlation between the photoelectron and photoion. It is shown that the coherent hole dynamics in Ar associated with a superposition of the spin-orbit states can be observed by using a Fourier-transform limited laser pulse for ionization, while the coherence is degraded or lost by chirping a laser pulse. We demonstrate that the coherent hole dynamics can be retrieved even in the case of a chirped laser pulse, by labeling the photoion dynamics with the counterpart photoelectron energy.
Sasaki, Akira; Murakami, Izumi*
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(17), p.175701_1 - 175701_11, 2013/09
The fractional ion abundance and rates of ionization and recombination of multiple charged tungsten ions in magnetic fusion plasmas are investigated using a collisional radiative model. Using a computer algorithm to generate a complete set of atomic states to be included into the collisional radiative model, the level population and ion abundance are calculated taking a sufficient number of dieletronic recombination and excitation autoionization channels into account. The atomic data, such as energy levels and rates of radiative decay as well as autoionization are provided from the ab-initio calculation using the HULLAC. The ion abundance is shown to converge with respect to the size of the model in the temperature range of 100 eV to 5 keV, and the ratio between the abundances of W and W ions agrees well with an experimental result obtained without any artificial adjustment of atomic rates.
Shigemasa, Eiji*; Nagasono, Mitsuru*; Iwayama, Hiroshi*; Harries, J.; Ishikawa, Lisa*
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164020_1 - 164020_5, 2013/08
Harries, J.; Nagasono, Mitsuru*; Iwayama, Hiroshi*; Shigemasa, Eiji*
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164021_1 - 164021_5, 2013/08
Yabashi, Makina*; Tanaka, Hitoshi*; Tanaka, Takashi*; Tomizawa, Hiromitsu*; Togashi, Tadashi*; Nagasono, Mitsuru*; Ishikawa, Tetsuya*; Harries, J.; Hikosaka, Yasumasa*; Hishikawa, Akiyoshi*; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164001_1 - 164001_19, 2013/08
Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Togashi, Tadashi*; Fukami, Kenji*; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164006_1 - 164006_6, 2013/08
By introducing 13th- (61.7 nm) and 15th-order harmonics (53.4 nm) of femtosecond laser pulses at 800 nm into an undulator of SCSS (SPring-8 Compact SASE Source) test accelerator at RIKEN, these harmonic pulses were amplified by a factor of more than 10 with a high contrast ratio through the interaction between accelerated electron bunches and the harmonic pulses. From numerical simulations of the amplification processes of high-order harmonic pulses in the undulator, optimum conditions of the electron bunch duration interacting with the high-order harmonic pulses were investigated for generating full-coherent and intense pulses in the extreme ultraviolet wavelength region.
Gejo, Tatsuo*; Ikegami, Takeshi*; Homma, Kenji*; Harries, J.; Tamenori, Yusuke*
Journal of Physics B; Atomic, Molecular and Optical Physics, 46(7), p.075102_1 - 075102_9, 2013/04
Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*; Itakura, Ryuji
Journal of Physics B; Atomic, Molecular and Optical Physics, 44(19), p.191002_1 - 191002_5, 2011/10
Ionization and subsequent electronic excitation occurring within the same laser pulse (400 nm, 96 fs, 1.318 TW/cm) are separately investigated by measuring in coincidence an electron and a product ion produced from CHOH. We reveal that the nascent population in the electronically excited CHOH prepared by the ionization decreases as the laser intensity increases, while the subsequent electronic excitation is enhanced through the resonant electronic transitions. Ionization and electronic excitation mechanisms are described based on the electronic state distributions of CHOH.
Sato, Takahiro*; Iwasaki, Atsushi*; Ishibashi, Kazuki*; Okino, Tomoya*; Yamanouchi, Kaoru*; Adachi, Junichi*; Yagishita, Akira*; Yazawa, Hiroki*; Kannari, Fumihiko*; Aoyama, Makoto; et al.
Journal of Physics B; Atomic, Molecular and Optical Physics, 44(16), p.161001_1 - 161001_5, 2011/08
The resonant and non-resonant two-photon single ionization processes of He were investigated using intense free electron laser light in the extreme ultraviolet (XUV) region (53.4-61.4 nm) covering the 1s-2p and 1s-3p resonant transitions of He. On the basis of the dependences of the yield of He on the XUV light-field intensity at 53.4, 58.4, 56.0 and 61.4 nm, the absolute values of the two-photon ionization cross sections of He at the four different wavelengths and their dependence on the light-field intensity were determined for the first time.
Harries, J.; Gejo, Tatsuo*; Homma, Kenji*; Kuniwake, Miki*; Sullivan, J. P.*; Lebech, M.*; Azuma, Yoshiro*
Journal of Physics B; Atomic, Molecular and Optical Physics, 44(9), p.095101_1 - 095101_7, 2011/05
Journal of Physics B; Atomic, Molecular and Optical Physics, 43(16), p.165602_1 - 165602_7, 2010/08
Yanagibayashi, Jun*; Nakano, Tomohide; Iwamae, Atsushi; Kubo, Hirotaka; Hasuo, Masahiro*; Itami, Kiyoshi
Journal of Physics B; Atomic, Molecular and Optical Physics, 43(14), p.144013_1 - 144013_6, 2010/07
We observe the vacuum ultraviolet spectra of highly charged tungsten ions in plasmas at electron temperatures of 8 keV and 14 keV. The observed emission lines in a wavelength range of 2.6 3.2 nm for the plasma at 8 keV are identified to be the transitions of . The observed emission lines at 2.0 nm and 2.3 nm at 14 keV are identified to be the transitions of and transitions of , respectively.
Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki
Journal of Physics B; Atomic, Molecular and Optical Physics, 43(14), p.144014_1 - 144014_7, 2010/00
The temporal evolutions of the electron temperature and density with ELM, determined from intensity ratios of the three He I lines measured at 20 kHz, start to increase 450 s before the peak of intensity, which is an ELM indicator. At the peak of intensity, the electron temperature starts to decrease while the electron density starts to decrease in 300 s. The temporal evolution of the electron temperature is ascribed to heating by the ELM plasma and to energy loss for ionization of recycled neutrals, and that of the electron density is ascribed to electrons supplied in the ionization of the neutrals.
Journal of Physics B; Atomic, Molecular and Optical Physics, 41(8), p.085602_1 - 085602_6, 2008/04
Moribayashi, Kengo; Kagawa, Takashi*; Kim, D. E.*
Journal of Physics B; Atomic, Molecular and Optical Physics, 38(13), p.2187 - 2194, 2005/07
no abstracts in English
Moribayashi, Kengo; Kagawa, Takashi*; Kim, D. E.*
Journal of Physics B; Atomic, Molecular and Optical Physics, 37(20), p.4119 - 4126, 2004/10
no abstracts in English