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
Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Jung, H. S.*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.
Nuclear Instruments and Methods in Physics Research B, 376, p.379 - 381, 2016/06
Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Katayama, Ichiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.
Japanese Journal of Applied Physics, 53(11), p.110303_1 - 110303_4, 2014/11
Kim, H.-S.*; Jeon, Y. M.*; Na, Y.-S.*; Ghim, Y.-C.*; Ahn, J.-W.*; Yoon, S. W.*; Bak, J. G.*; Bae, Y. S.*; Kim, J. S.*; Joung, M.*; et al.
Nuclear Fusion, 54(8), p.083012_1 - 083012_11, 2014/08
We evaluate the characteristics of global energy confinement in KSTAR () quantitatively by comparing it with multi-machine scalings, by deriving multiple regression equations for the L- and the H-mode plasmas, and evaluating confinement enhancement of the H-mode phase compared with the L-mode phase in each discharge. From the KSTAR database, of L-mode plasmas exhibits s to s and of H-mode plasmas s to s. The multiple regression equations derived by statistical analysis present the similar dependency on PL and slightly higher dependency on IP compared with the multi-machine scalings, however the dependency on elongation in both L- and H-mode plasmas draw the negative power dependency of and for H-mode and for L- mode database, respectively on the contrary to the positive dependency in all multi-machine empirical scalings. Although the reason is not clear yet, two possibilities are addressed. One is that the wall condition of KSTAR was not clean enough. The other is that striking points on the divertor plate were uncontrolled. For these reasons, as increases, the impurities from the wall can penetrate into plasmas easily. As a consequence, the confinement is degraded on the contrary to the expectation of multi-machine scalings.
Sonoda, Tetsu*; Wada, Michiharu*; Tomita, Hideo*; Sakamoto, Chika*; Takatsuka, Takaaki*; Furukawa, Takeshi*; Iimura, Hideki; Ito, Yuta*; Kubo, Toshiyuki*; Matsuo, Yukari*; et al.
Nuclear Instruments and Methods in Physics Research B, 295, p.1 - 10, 2013/01
no abstracts in English
Hirayama, Yoshikazu*; Mihara, Mototsugu*; Watanabe, Yutaka*; Jeong, S. C.*; Miyatake, Hiroari*; Momota, Sadao*; Hashimoto, Takashi*; Imai, Nobuaki*; Matsuta, Kensaku*; Ishiyama, Hironobu*; et al.
European Physical Journal A, 48(5), p.54_1 - 54_10, 2012/05
Ishiyama, Hironobu*; Yamaguchi, Kanako*; Mizoi, Yutaka*; Watanabe, Yutaka*; Das, S. K.*; Hashimoto, Takashi*; Miyatake, Hiroari*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Oyaizu, Mitsuhiro*; et al.
Journal of Instrumentation (Internet), 7(3), p.C03036_1 - C03036_14, 2012/03
We developed an active-target type gas counter operating with low He/CO (10%) detector gas for application in studying low-energy nuclear reactions using radioactive beams. A 400-m-thick gas electron multiplier (THGEM) was used as the proportional counter for high injection rate capability. We examined the gas gain stability and the influence of ion feedback on particle tracks at high beam injection rates of up to 10 particles per second (pps) using a low-energy C beam. From the result of this examination, we found that the THGEM was found to be applicable for our active target at high injection rates of up to 10 pps.
Okada, Masashi*; Niki, Kazuaki*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Ishiyama, Hironobu*; Jeong, S. C.*; Katayama, Ichiro*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Watanabe, Yutaka*; et al.
Physical Review Special Topics; Accelerators and Beams, 15(3), p.030101_1 - 030101_10, 2012/03
Watanabe, Kazuhiro; Dairaku, Masayuki; Tobari, Hiroyuki; Kashiwagi, Mieko; Inoue, Takashi; Hanada, Masaya; Jeong, S. H.*; Chang, D. H.*; Kim, T. S.*; Kim, B. R.*; et al.
Review of Scientific Instruments, 82(6), p.063507_1 - 063507_6, 2011/06
A long pulse plasma generator for neutral beam injectors has been developed. The plasma generator was designed to produce 65 A at 120 keV from a beam extraction area of 12 cm 46 cm. A type of the plasma generator is a multi-cusp plasma generator with SmCo permanent magnets. A long pulse test of the plasma generator was performed at the KSTAR NBI test stand in Korea under the Japan - Korea Fusion collaboration. It was successfully demonstrated of the long pulse operation of the plasma generator for 200 s at an arc discharge power of 70 kW which can produce 65 A beams. Plasma spatial uniformity at the beam extraction area was confirmed to be smaller than 8% of the deviation from an averaged ion saturation current density. A high arc efficiency of 0.9-1.1 A/kW was obtained at the beam extraction with 73 keV, 41 A for 5 sec. From these experimental studies, a performance of this plasma generator for long pulse ion sources was confirmed.
Yang, H. L.*; Kim, Y. S.*; Park, Y. M.*; Bae, Y. S.*; Kim, H. K.*; Kim, K. M.*; Lee, K. S.*; Kim, H. T.*; Bang, E. N.*; Joung, M.*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Because the 2010 operation of Korea Superconducting Tokamak Advanced Research (KSTAR) mainly aims to achieve strongly elongated and diverted plasma, all the necessary hardware systems to provide an essential circumstance for the plasma shaping were newly installed and upgraded in 2010. In this paper, general configuration of the upgraded systems described earlier will be outlined. Moreover, several key performances and test results of the systems will be also reported in summary.
Imai, Nobuaki*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Jeong, S.-C.*; Miyatake, Hiroari*; Watanabe, Yutaka*; Makii, Hiroyuki; Mitsuoka, Shinichi; Nagae, Daisuke*; Nishinaka, Ichiro; et al.
European Physical Journal A, 46(2), p.157 - 160, 2010/11
Stober, J.*; Jackson, G. L.*; Ascasibar, E.*; Bae, Y.-S.*; Bucalossi, J.*; Cappa, A.*; Casper, T.*; Cho, M. H.*; Gribov, Y.*; Granucci, G.*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2010/10
Mitsuoka, Shinichi; Ikezoe, Hiroshi; Nishio, Katsuhisa; Watanabe, Yutaka*; Jeong, S. C.*; Ishiyama, Hironobu*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari
International Journal of Modern Physics E, 19(5&6), p.989 - 996, 2010/07
We have measured quasi-elastic scattering cross sections in reactions of Ti, Cr, Fe, Ni and Zn + Pb, relating to Pb-based cold fusion reactions for super-heavy elements 104, 106, 108, 110 and 112, respectively. A thin target of Pb was bombarded by heavy-ion beams supplied from the JAEA tandem-booster accelerator with changing the beam energy in steps of 1.5 MeV. The barrier distributions were derived from the first derivative of the excitation functions measured at backward angles of 172, 168 and 162. The centroid of the barrier distributions showed a deviation from several predicted barrier heights toward the low energy side. The shape of the barrier distributions was well reproduced by the results of a coupled-channel calculation taking account of the coupling effects of the collective vibrational excitations in the projectile and target nuclei. We have recently obtained similar results in heavier reactions of Ge and Kr + Pb.
Ikezoe, Hiroshi; Mitsuoka, Shinichi; Nishio, Katsuhisa; Watanabe, Yutaka*; Jeong, S. C.*; Otsuki, Tsutomu*; Hirose, Kentaro*
Nuclear Physics A, 834(1-4), p.172c - 175c, 2010/03
The Coulomb barrier distribution between heavy nuclei is important quantity to investigate the effect of quantum couplings of nuclear vibration and nucleon transfer to nucleus-nucleus interaction. We obtained the barrier distributions of lead-based fusion reactions of Ti, Cr, Fe, Ni, Zn, Ge, and Kr projectiles on Pb by means of the measurements of the quasi-elastic cross sections at backward scattering angles. The obtained positions and widths of the barrier distributions are compared with a calculation taking account of the channel couplings. The effect of the nuclear deformation on reaction process was also investigated by means of the measurements of product mass distributions for the systems of Si, S, Ar projectiles on U. We found that the collision at polar side gives rise to quasi-fission, where an asymmetric fission is dominant.
Jeong, S.-C.*; Sugai, Hiroyuki; Yahagi, Masahito*
Nippon Butsuri Gakkai-Shi, 64(9), p.687 - 691, 2009/09
We have demonstrated a non-destructive and on-line radiotracer method for diffusion studies in lithium ionic conductors, by using, as a tracer, the short-lived alpha-emitting radioisotope of Li from TRIAC (Tokai Radioactive Ion Accelerator Complex). The method has been successfully applied to measure the lithium diffusion coefficients in a typical defect-mediated lithium ionic conductor of LiGa, well demonstrating that the method is very effective to measure the diffusion in the micrometer regime per second. Anomalous composition-dependence of Li diffusion coefficients in LiGa was observed. The anomaly was discussed qualitatively in terms of the formation of defect complex and the interaction between the constituent defects. The ordering of the Li vacancies in the Li-deficient LiGa was observed for the first time in terms of the Li diffusion by the present method, and its thermodynamic aspect was discussed.
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
The excitation function of the Li(d,t)Li reaction was directly measured using Li beams at E = 0.3, 0.4, 0.5, 0.7, 0.8, 1.0, 1.1, and 1.2 MeV with CD targets. The beam energies covered the Gamow peaks for 1310 K. Large cross sections were observed at around E = 0.8 MeV, implying a resonance state located at 22.4 MeV in Be. The present astrophysical reaction rate is higher in one order magnitude than the presently adopted rate at around 110 K.
Osa, Akihiko; Ichikawa, Shinichi; Matsuda, Makoto; Sato, Tetsuya; Jeong, S.-C.*
Nuclear Instruments and Methods in Physics Research B, 266(19-20), p.4394 - 4397, 2008/10
Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Imai, Nobuaki*; Hirayama, Yoshikazu*; Miyatake, Hiroari; Sataka, Masao; Sugai, Hiroyuki; et al.
Japanese Journal of Applied Physics, 47(8), p.6413 - 6415, 2008/08
A non-destructive and on-line diffusion tracing in Li ionic conductors has been demonstrated. As a tracer, pulsed beam of Li was implanted into LiGa. By analyzing the time dependent yield of the -particles decaying from Li, diffusion coefficients were extracted with a high accuracy. The ordering of Li vacancies in the Li-deficient phase of LiGa was observed for the first time in terms of the Li diffusion.
Nishiuchi, Mamiko; Daido, Hiroyuki; Yogo, Akifumi; Orimo, Satoshi; Ogura, Koichi; Ma, J.-L.; Sagisaka, Akito; Mori, Michiaki; Pirozhkov, A. S.; Kiriyama, Hiromitsu; et al.
Physics of Plasmas, 15(5), p.053104_1 - 053104_10, 2008/05
High-flux energetic protons whose maximum energies are up to 4 MeV are generated by an intense femtosecond Titanium Sapphire laser pulse interacting with a 7.5, 12.5, and 25m thick Polyimide tape targets. The laser pulse energy is 1.7 J, duration is 34 fs, and intensity is 310Wcm. The amplified spontaneous emission (ASE) has the intensity contrast ratio of 410. The conversion efficiency from laser energy into proton kinetic energies of 3% is achieved, which is comparable or even higher than those achieved in the previous works with nanometer-thick targets and the ultrahigh contrast laser pulses (10).
Imai, Nobuaki*; Jeong, S.-C.*; Oyaizu, Mitsuhiro*; Arai, Shigeaki*; Fuchi, Yoshihide*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Miyatake, Hiroari; Tanaka, Masahiko*; Okada, Masayuki*; et al.
Review of Scientific Instruments, 79(2), p.02A906_1 - 02A906_3, 2008/02
KEKCB is an 18 GHz Electron Cyclotron Resonance (ECR) ion source and is a charge breeder device for converting mass-separated 1 radioactive ions to multi-ionized ones by utilizing an axial injection technique to the ECR plasma. It is a part of the Tokai Radioactive Ion Accelerator Complex (TRIAC) facility. Based on the developments so far, converting efficiencies for metal elements, such as barium and indium, and for gaseous elements, such as krypton and xenon, are improved to be 7 and 2 , respectively. And it is confirmed that the efficiency is nearly the constant for short-lived (t 1 sec) isotopes. Background ions mixed in the output beams are supressed to be 600 pps from 10 pps by applying all aluminum electrodes and high pressure pure-water cleanings.