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Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:9 Percentile:88.96(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Towards a novel laser-driven method of exotic nuclei extraction-acceleration for fundamental physics and technology

Nishiuchi, Mamiko*; Sakaki, Hironao*; Esirkepov, T. Zh.*; Nishio, Katsuhisa; Pikuz, T. A.*; Faenov, A. Ya.*; Skobelev, I. Yu.*; Orlandi, R.; Pirozhkov, A. S.*; Sagisaka, Akito*; et al.

Plasma Physics Reports, 42(4), p.327 - 337, 2016/04

 Times Cited Count:9 Percentile:57.29(Physics, Fluids & Plasmas)

A combination of a petawatt laser and nuclear physics techniques can crucially facilitate the measurement of exotic nuclei properties. With numerical simulations and laser-driven experiments we show prospects for the Laser-driven Exotic Nuclei extraction-acceleration method proposed in [M. Nishiuchi et al., Phys. Plasmas 22, 033107 (2015)]: a femtosecond petawatt laser, irradiating a target bombarded by an external ion beam, extracts from the target and accelerates to few GeV highly charged short-lived heavy exotic nuclei created in the target via nuclear reactions.

Journal Articles

Acceleration of highly charged GeV Fe ions from a low-Z substrate by intense femtosecond laser

Nishiuchi, Mamiko; Sakaki, Hironao; Esirkepov, T. Z.; Nishio, Katsuhisa; Pikuz, T.*; Faenov, A.*; Skobelev, I. Yu.*; Orlandi, R.; Sako, Hiroyuki; Pirozhkov, A. S.; et al.

Physics of Plasmas, 22(3), p.033107_1 - 033107_8, 2015/03

 Times Cited Count:60 Percentile:97.99(Physics, Fluids & Plasmas)

Almost fully stripped Fe ions accelerated up to 0.9 GeV are demonstrated with a 200 TW femtosecond high-intensity laser irradiating a micron-thick Al foil with Fe impurity on the surface. An energetic low-emittance high-density beam of heavy ions with a large charge-to-mass ratio can be obtained, which is useful for many applications, such as a compact radio isotope source in combination with conventional technology.

Journal Articles

A Phase-field simulation of uranium dendrite growth on the cathode in the electrorefining process

Shibuta, Yasushi*; Unoura, Seiji*; Sato, Takumi; Shibata, Hiroki; Kurata, Masaki*; Suzuki, Toshio*

Journal of Nuclear Materials, 414(2), p.114 - 119, 2011/07

 Times Cited Count:10 Percentile:65.84(Materials Science, Multidisciplinary)

The uranium dendrite growth on cathode during pyroprocessing of uranium is investigated using a novel phase-field model, in which electrodeposition of uranium and zirconium from molten-salt is taken into account. The threshold concentration of zirconium in molten salt demarcating the dendritic and planar growth is then estimated as a function of the current density. Moreover, growth process of both the dendritic and planar electrodeposits has been demonstrated by way of varying the mobility of the phase field, which consists of the effect of attachment kinetics and diffusion.

Journal Articles

Dissociation and recapture dynamics in H$$_2$$O following O 1s inner-shell excitation

Gejo, Tatsuo*; Oura, Masaki*; Kuniwake, Miki*; Homma, Kenji*; Harries, J.

Journal of Physics; Conference Series, 288, p.012023_1 - 012023_7, 2011/04

 Times Cited Count:11 Percentile:93.75

In this paper we present a study of the dissociation dynamics following O 1s inner-shell excitation/ionization in the water molecule. When the O 1s electron is excited just below or just above the ionization threshold, neutral fragments are created. Information on the electronic states of these fragments provides information on the dissociation dynamics. Excitation of the O 1s electron creates a H$$_2$$O$$^+$$ ionic core, which is unstable and undergoes Auger decay. The resulting H$$_2$$O$$^{2+}$$ ion core subsequently dissociates into 2 or three fragments, to one of which the initially excited electron attaches. If this fragment is O$$^+$$ or OH$$^+$$, a neutral, excited O atom can be created. This fragment can undergo further Auger (autoionisation) decay. Here we have analysed the kinetic energy distribution of both these low energy electrons and also the initial high energy Auger electron, obtaining new information on the processes involved.

Journal Articles

The 1s-2p resonance photoionization measurement of O$$^{+}$$ ions in comparison with an isoelectronic species Ne$$^{3+}$$

Kawatsura, Kiyoshi*; Yamaoka, Hitoshi*; Oura, Masaki*; Hayaishi, T.*; Sekioka, T.*; Agui, Akane; Yoshigoe, Akitaka; Koike, Fumihiro*

Journal of Physics B; Atomic, Molecular and Optical Physics, 35(20), p.4147 - 4153, 2002/10

 Times Cited Count:21 Percentile:66.85(Optics)

no abstracts in English

Journal Articles

Photoionization of Ne$$^{3+}$$ ions in the region of the 1${it s}$ $$rightarrow$$ 2${it p}$ autoionizing resonance

Oura, Masaki*; Yamaoka, Hitoshi*; Kawatsura, Kiyoshi*; Kimata, Junichi*; Hayaishi, T.*; Takahashi, Takehisa*; Koizumi, Tetsuo*; Sekioka, T.*; Terasawa, Michitaka*; Ito, Yo*; et al.

Physical Review A, 63(1), p.014704_1 - 014704_4, 2001/01

 Times Cited Count:15 Percentile:61.17(Optics)

no abstracts in English

Journal Articles

L X-ray spectra of Fe and Cu by 0.75 MeV/u H, He, Si and Ar ion impacts

Kageyama, H.*; Kawatsura, Kiyoshi*; Takahashi, R.*; Arai, Shigeyoshi*; Kambara, Tadashi*; Oura, Masaki*; Papp, T.*; Kanai, Yasuyuki*; Awaya, Yoko*; Takeshita, Hidefumi; et al.

Nuclear Instruments and Methods in Physics Research B, 107(1-4), p.47 - 50, 1996/00

 Times Cited Count:2 Percentile:32.32(Instruments & Instrumentation)

no abstracts in English

Oral presentation

Photodissociation dynamics of water in K-edge energy region

Gejo, Tatsuo*; Kuniwake, Miki*; Homma, Kenji*; Harries, J.; Oura, Masaki*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

Exciting an inner-shell electron of a molecule to just-above or just-below its ionisation limit provides a system where the Born-Oppenheimer principle is no longer valid, and a valuable opportunity for studying the interaction of the unstable ion core and a low-energy electron. When the ion core undergoes Auger decay and fragments, the initially excited electron can be recaptured. It is the aim of this research to understand what happens in the case of the water molecule, by (1) detecting excited H atoms produced when the electron is captured by an outgoing proton. (2) detect the Lyman-$$alpha$$ radiation produced when these excited H atoms decay, and (3) analysing the energy of low-energy Auger electrons emitted when the electron is captured by an O$$^+$$ or O$$^{++}$$ fragment.

Oral presentation

O(1s) photodissociation dynamics of gas-phase H$$_2$$O

Harries, J.; Gejo, Tatsuo*; Kuniwake, Miki*; Homma, Kenji*; Oura, Masaki*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

Photo-excitation of the O 1s electron in H$$_2$$O can lead to the production of neutral, excited H atoms. Knowledge of the excited state distribution provides information on the dissociation dynamics process. Excitation of the O 1s electron leads to a H$$_2$$O$$^+$$ ion core. Auger decay subsequently leads to H$$_2$$O$$^{2+}$$, which dissociates, and one of the fragments can capture the initially excited electron. If this fragment is H$$^+$$, excited neutral H atoms are formed. In this research we use pulsed synchrotron radiation as the excitation source, and detect the UV fluorescence emitted when the excited H atoms decay. Analysis of the decay lifetimes leads to information on the excited state distribution.

Oral presentation

The Photodissociation dynamics of H$$_2$$O after recapture process via Auger decay of O 1s inner-shell excitation

Gejo, Tatsuo*; Oura, Masaki*; Kuniwake, Miki*; Homma, Kenji*; Harries, J.

no journal, , 

In this research we have obtained new information on the photo-dissociation dynamics of the water molecule following O (1s) inner-shell excitation/ionisation. When the O 1s electron is excited as well as neutral excited H atoms, highly-excited O and OH fragments can also be produced. By investigating which states these fragments are in information can be obtained on the dissociation routes. When the inner-shell O 1s electron is excited/ionised, an H$$_2$$O$$^+$$ ion core is formed. This is unstable, and Auger decay occurs. The resulting H$$_2$$O$$^{2+}$$ ion core dissociates, and one of the fragments can capture the initially excited electron. When this fragment is O$$^+$$, a neutral O atom is formed. This fragment can undergo further Auger decay, resulting in the production of an electron with low kinetic energy. In this research these electrons are detected and energy analysed.

Oral presentation

Multi-charged heavy ion acceleration from the ultra-intense short pulse laser system interacting with the metal target

Nishiuchi, Mamiko; Sakaki, Hironao; Nishio, Katsuhisa; Sako, Hiroyuki; Orlandi, R.; Pikuz, T.; Faenov, A.*; Esirkepov, T. Z.; Pirozhkov, A. S.; Matsukawa, Kenya*; et al.

no journal, , 

To investigate the quark-gruon plasma or the systhesis of the super-heavy elements, the upgrade of the existing large accelerator facilities are going on. At J-PARC, the high flux high energy heavy ion beam is also desired. To have the beam, it is key issue how to obtain the high Q/M heavy ions a the ion source. However, the conventional ion source technique have difficulties to obtain such ions. On the other hand, we succeeded to obtain the high Q/M heavy ion beam with $$>$$ 10 MeV/u from the interaction between the J-KAREN laser and thin foil target interaction. This results shows that the laser-driven ion acceleration scheme have possibility that it can substitute the conventional ion source as well as the injector.

Oral presentation

Laser-driven ion acceleration by high intensity short-pulse high-contrast laser system at JAEA

Nishiuchi, Mamiko; Sakaki, Hironao; Nishio, Katsuhisa; Orlandi, R.; Sako, Hiroyuki; Pikuz, T.; Faenov, A. Ya.*; Esirkepov, T. Z.; Pirozhkov, A. S.; Matsukawa, Kenya*; et al.

no journal, , 

For the applications of compact injector, we conduct the ion acceleration experiments using relatively compact and high-contrast short pulse laser system, J-KAREN at KPSI JAEA. The on-target laser intensity of 10$$^{21}$$ Wcm$$^{-2}$$ with 200TW, less than 10J of energy, is achieved by controlling the temporal and spatial pulse profiles. Without applying plasma mirror system, the maximum proton energy of 43 MeV is obtained with aluminum (Al) 0.8 um thick target. In some shots we observe that the protons and Al ions are accelerated up to 30 MeV and 12 MeV/u, respectively. With the soft X-ray spectroscopy the Al ions are found to be almost fully stripped, which is caused by the synergy of three major effects: optical field ionization due to the laser and plasma collective fields; the electron impact ionization; and the X-ray single photon ionization. The observation of almost fully stripped Al ions proves that laser-driven ions acceleration is a promising ion source for the conventional accelerator. In addition, the observed energy of 12 MeV/u of the Al ions shows that the laser-based ion acceleration method can be the basis of a compact heavy ion injector for nuclear physics.

Oral presentation

Ion acceleration by the 10$$^{21}$$ Wcm$$^{-2}$$ intensity high contrast laser pulses interacting with the thin foil target

Nishiuchi, Mamiko; Sakaki, Hironao; Nishio, Katsuhisa; Orlandi, R.; Sako, Hiroyuki; Pikuz, T.; Faenov, A. Ya.*; Esirkepov, T. Z.; Pirozhkov, A. S.; Matsukawa, Kenya*; et al.

no journal, , 

Laser-driven ion beam is paid attention because of its peculiar characteristics. One of the applications is the compact injector for the conventional accelerator system for the nuclear research. For that objective, we have carried out the J-KAREN experiment with 10$$^{21}$$ Wcm$$^{-2}$$ of intensity, less than 10 J of energy and 35fs of laser duration with 10$$^{10}$$ contrast level. The J-KAREN laser pulses are irradiated on the Al foil target. Almost fully stripped aluminum ion acceleration up to 12 MeV/u from the interaction between the ultra-intense short pulse high contrast laser and the micrometer thick foil target is presented.

Oral presentation

Laser-driven heavy ion acceleration and its applications

Sakaki, Hironao; Nishiuchi, Mamiko; Esirkepov, T. Z.; Nishio, Katsuhisa; Pikuz, T. A.*; Faenov, A.*; Orlandi, R.; Pirozhkov, A. S.; Sako, Hiroyuki; Sagisaka, Akito; et al.

no journal, , 

The novel tool for the frontier of the exotic nucleus was proposed by fusing the high-intensity laser technology and the accelerator technology. We carried out its proof-of-concept experiments at the J-KAREN laser system. And, the iron which is simulated the produced exotic nucleus were extracted by the laser from aluminum membrane.

Oral presentation

Proof of principle experiment of laser-driven exotic nuclei extraction-acceleration method

Nishiuchi, Mamiko; Sakaki, Hironao; Nishio, Katsuhisa; Orlandi, R.; Sako, Hiroyuki; Pikuz, T. A.*; Faenov, A. Ya.*; Esirkepov, T. Z.; Pirozhkov, A. S.; Matsukawa, Kenya*; et al.

no journal, , 

The contemporary radiofrequency accelerator technology provides radio-isotope beams for the research. However, the existing technology now faces difficulties in exploring the further frontiers. One of the solutions might be brought by the combination of the state of the art high intensity short pulse laser system and the nuclear measurement technique. Recent progress of the laser technology brought table-top lasers with focused intensity up to 10$$^{21}$$ Wcm$$^{-2}$$ with only less than 10 J of energy on target. By the interaction with the solid density target, the laser can extract heavy ions in multi-charged state and low emittance, independently on the chemical properties of the target material. We propose Laser-driven Exotic Nuclei extraction-acceleration methods (LENex), in which the exotic nuclei which are the products in the target by the bombardment of the external ion beam, are extracted away by a femtosecond petawatt laser pulse in the form of highly-charged and high energy beam. As a proof-of-experiment of the LENex scheme, we demonstrate the extraction of the almost fully stripped iron ions with the energies of 0.9 GeV by J-KAREN laser system.

Oral presentation

Proof of principle experiment of Laser-driven Exotic Nuclei extraction-acceleration method

Nishiuchi, Mamiko; Sakaki, Hironao; Nishio, Katsuhisa; Orlandi, R.; Sako, Hiroyuki; Pikuz, T. A.*; Faenov, A. Ya.*; Esirkepov, T. Z.; Pirozhkov, A. S.; Matsukawa, Kenya*; et al.

no journal, , 

The contemporary radiofrequency accelerator technology provides radio-isotope beams for the research. However, the existing technology now faces difficulties in exploring the further frontiers. One of the solutions might be brought by the combination of the state of the art high intensity short pulse laser system and the nuclear measurement technique. Recent progress of the laser technology brought table-top lasers with focused intensity up to 10$$^{21}$$ Wcm$$^{-2}$$ with only less than 10 J of energy on target. By the interaction with the solid density target, the laser can extract heavy ions in multi-charged state and low emittance, independently on the chemical properties of the target material. We propose Laser-driven Exotic Nuclei extraction-acceleration methods (LENex), in which the exotic nuclei which are the products in the target by the bombardment of the external ion beam, are extracted away by a femtosecond petawatt laser pulse in the form of highly-charged and high energy beam. As a proof-of-experiment of the LENex scheme, we demonstrate the extraction of the almost fully stripped iron ions with the energies of 0.9 GeV. by J-KAREN laser system.

Oral presentation

The Millennium scale monsoon cycles recorded in a sediment core from alpine Tibetan lake

Watanabe, Takahiro; Nara, Fumiko*; Matsunaka, Tetsuya*; Minoura, Koji*; Kakegawa, Takeshi*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Nakamura, Toshio*; Junbo, W.*; Liping, Z.*

no journal, , 

Understanding of past environmental and geochemical changes is significant issues to estimate global climate variation. Therefore, these changes have been studied by continuous terrestrial sediments. The high-time resolution past environmental changes, especially monsoon fluctuations, have been reported in previous studies using geochemical signatures in stalagmites from Asian caves. However, continuous climate records in Tibetan plateau have not yet been cleared, which a key area to understand mechanism of monsoon fluctuations. In this study, mean grain size and geochemical proxies from lake sediment cores from south Tibetan plateau were used for estimation of past monsoon changes during Holocene. Spectral analysis of the mean grain size in the Tibetan lake indicated 1000-1500 years climate cycles, which might be caused by the changes in solar activities. These monsoon fluctuations based on the mean grain size were also supported by geochemical proxies in this study.

Oral presentation

Rb/Sr ratio in Lake Baikal sediment core; The New geochemical proxy for East Asian winter monsoon strength during cool climate period

Nara, Fumiko*; Yamasaki, Shinichi*; Watanabe, Takahiro; Tsuchiya, Noriyoshi*; Miyahara, Hiroko*; Kato, Takenori*; Minoura, Koji*; Kakegawa, Takeshi*

no journal, , 

High-time resolution measurements of the major and trace inorganic elements, such as Rb and Sr, from the Lake Baikal sediment core was carried out to estimate the weathering response and the material provenance in the lake watershed. The fluctuations of the Rb/Sr ratio and mean grain size (MGS) during the Holocene were corresponding with each other. The similar profiles between the Rb/Sr ratio and the MGS from loess sediment in China have been observed in previous study. These results imply that the Rb/Sr ratio can be used as the proxy to estimate the East Asian winter monsoon intensity.

19 (Records 1-19 displayed on this page)
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