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Observation of MHD Instabilities Driven by Energetic Electrons in the Large Helical Device

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Plasma Science and Technology 2015年第4期17卷 276-279页

作者： Mitsutaka ISOBE Kunihiro OGAWA Akihiro SHIMIZU Masaki OSAKABE shin kubo K.TOI the LHD Experiment Group National Institute for Fusion Science Toki 509-5292Japan Department of Fusion Science The Graduate University for Advanced Studies(SOKENDAI)Toki 509-5292Japan Department of Energy Engineering and Science Nagoya UniversityNagoya 464-8463Japan

Coherent magnetic fluctuations in an acoustic range of frequency have been regularly observed in low-density（n_e〈0.2×10^（19）m^（-3））plasmas with strong second harmonic electron cyclotron resonance heating（ECRH）on the Large Helical *** X-ray measurements indicated that energetic electrons are generated in these ECRH *** magnetic fluctuations are suppressed in higher density discharges where energetic electrons are not *** ECRH power modulation experiment indicated that the observed magnetohydrodynamic（MHD）mode has an acoustic nature rather than an Alfvenic nature.

关键词： LHD ECRH energetic electron MHD instability

Investigation of Experimental Con6guration for Electron Bernstein Wave Heating on LHD

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Plasma Science and Technology 2009年第4期11卷 430-438页

作者： Hiroe IGAMI Ryosuke IKEDA Hiromi TAKAHASHI Yasuo YOSHIMURA Takashi SHIMOZUMA shin kubo Hitoshi TANAKA Kazunobu NAGASAKI Takashi MUTOH the LHD Experiment Group National Institute for Fusion Science 509-5292 Toki Japan Graduate School of Energy Science Kyoto University 606-8502 Kyoto Japan Institute of Advanced Energy Kyoto University 611-0011 Uji Japan

Investigation of experimental configuration for the electron Bernstein wave （EBW） heating by using the existing electron cyclotron heating （ECH） antennas on LHD was performed. By using an antenna installed in the lower port, direct oblique launching of the extraordinary （X-） mode from the high magnetic field side （HFS） is available. Since the parallel component of the refractive index （NIF） varies during propagation because of the inhomogeneity of the magnetic field, NH can be zero when the launched X-mode crosses the fundamental electron cyclotron resonance （ECR） layer even NⅡ is noonzero initially. In such a condition, if the electron density is above a certain level the obliquely launched X-mode can pass the fundamental ECR layer without being damped out and can be mode-converted to EBW that is absorbed at the Doppler shifted ECR layer. By using an antenna installed in the horizontal port, oblique launching from the lower magnetic field side （LFS） toward the over-dense plasma is available. Excitation of EBW via the mode conversion process of ordinary mode（O）-extraordinary mode（X）-electron Bernstein wave （B） is expected with the O-mode launching toward an appropriate direction. The O-X-B mode conversion rate and the region of power deposition were surveyed by varying the magnetic field strength and the launching direction. The results of the survey suggest that efficient heating in the core region is difficult by using the existing antenna. Rearrangement of the final mirror of the launching antenna may be needed.

关键词： LHD electron cyclotron heating (ECH) electron Bernstein wave (EBW),high density plasma

Development of a Heavy Ion Bearn Probe for Measuring Electrostatic Potential Profile and Its Fluctuation in LHD

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Plasma Science and Technology 2009年第4期11卷 460-464页

作者： TakeshiI DO Akihiro SHIMIZU Masaki NISHIURA Haruhisa NAKANO shinji KATO shinsuke OHSHIMA Yasuo YOSHIMURA shin kubo Takashi SHIMOZUMA HiroeI GAMI Hiromi TAKAHASHI Kazuo TOI Fumitake WATANABE Kazumichi NARIHARA Ichihiro YAMADA National Institute for Fusion Science

A heavy ion beam probe （HIBP） using a 3-MV tandem accelerator has been installed on large helical device （LHD）. Electrostatic potential in core plasma can be measured under the toroidal magnetic field strength of up to 3 T. By using the HIBP, the transition of potential profiles from electron-root to ion^root is observed in core plasmas during ramp-up of the electron density. Potential fluctuations are also measured electron cyclotron current drive （ECCD）. Two kind of characteristic fluctuations are observed. One is a reversed-shear-induced Alfv^n eigenmode （RSAE）, whose frequency varies during the evolution of the rotational transform profile, and the other is with a constant geodeisc acoustic mode （GAM） frequency.

关键词： electrostatic potential measurement HIBP GAM RSAE

Study of High Power ICRF Antenna Design in LHD

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Plasma Science and Technology 2010年第1期12卷 15-19页

作者： Hiroshi KASAHARA Tetsuo SEKI Kenji SAITO Ryuhei KUMAZAWA Takashi MUTOH Goro NOMURA Fujio SHIMPO shin kubo Takashi SHIMOZUMA Yasuo YOSHIMURA Hiroe IGAMI Hiromi TAKAHASHI 赵燕平 Takuya OOSAKO Yuichi TAKASE National Institute for Fusion Science Institute of Plasma Physics Chinese Academy of Sciences University of Tokyo

In large helical device （LHD）, antenna loadings are different for minority ion cyclotron heating （MICH with 38.47 MHz） and mode-converted ion Bernstein wave heating （MC-IBW with 28.4 MHz）, and it is necessary to improve antenna loading with low heating efficiency to avoid arching on transmission line. To design a new ion cyclotron range of frequencies （ICRF） antenna in LHD, calculation for a simple antenna model is conducted using three-dimensional electrical magnetic code （high frequency structure simulator, HFSS） for an water loading as an imaginary plasma with low heating efficiency. At resonant frequencies, antenna loading is sensitive to strap width, and resonant frequencies are strongly related to strap height. There is no differences of RF current profile on the strap surface between resonant frequency and non-resonant frequency. The strap should be perpendicularly placed against the magnetic field line, since Faraday-shield angle will lead to a decrease in the effective antenna height.

关键词： ICRF minority heating mode conversion heating antenna design LHD

Recent advances in endoscopic ultrasonography-guided biliary interventions

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World Journal of Gastroenterology 2015年第32期21卷 9494-9502页

作者： Kazumichi Kawakubo Hiroshi Kawakami Masaki Kuwatani shin Haba Shuhei Kawahata Yoko Abe Yoshimasa kubota Kimitoshi kubo Hiroyuki Isayama Naoya Sakamoto Department of Gastroenterology and Hepatology Hokkaido University Graduate School of Medicine Department of Gastroenterology Graduate School of Medicine The University of Tokyo

Interventional endoscopic ultrasonography(EUS) based on EUS-guided fine-needle aspiration has rapidly spread as a minimally invasive procedure. Especially in patients with failed endoscopic retrograde cholangiopancreatography, EUS-guided biliary intervention is reported to be useful as salvage therapy. EUS-guided biliary interventions are carried out using three techniques: EUS-guided bilioenteric anastomosis, EUS-guided rendezvous procedure, and EUS-guided antegrade treatment. Although interventional EUS is not yet a standardized procedure, there have been recent advances in this field that address various biliary diseases. Here, we summarize the indications, techniques, clinical results of previous studies, and future perspectives.

关键词： Endosonography-guided biliary intervention Choledo

Retrospective cohort study Lower incidence of complications in endoscopic nasobiliary drainage for hilar cholangiocarcinoma

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World Journal of Gastrointestinal Endoscopy 2016年第9期8卷 385-390页

作者： Kazumichi Kawakubo Hiroshi Kawakami Masaki Kuwatani shin Haba Taiki Kudo Yoko A Taya Shuhei Kawahata Yoshimasa kubota Kimitoshi kubo Kazunori Eto Nobuyuki Ehira Hiroaki Yamato Manabu Onodera Naoya Sakamoto Department of Gastroenterology and Hepatology Hokkaido University Graduate School of Medicine Sapporo 0608638Japan

AIM:To identify the most effective endoscopic biliary drainage technique for patients with hilar ***:In total,118 patients with hilar cholangiocarcinoma underwent endoscopic management[endoscopic nasobiliary drainage(ENBD)or endoscopic biliary stenting]as a temporary drainage in our institution between 2009 and *** retrospectively evaluated all complications from initial endoscopic drainage to surgery or palliative *** risk factors for biliary reintervention,post-endoscopic retrograde cholangiopancreatography(post-ERCP)pancreatitis,and percutaneous transhepatic biliary drainage(PTBD)were also analyzed using patient-and procedure-related *** risk factors for bilateral drainage were examined in a subgroup analysis of patients who underwent initial unilateral ***:In total,137 complications were observed in92(78%)*** reintervention was required in 83(70%)*** was significantly associated with a low risk of biliary reintervention[odds ratio(OR)=0.26,95%CI:0.08-0.76,P=0.012].Post-ERCP pancreatitis was observed in 19(16%)*** absence of endoscopic sphincterotomy was significantly associated with post-ERCP pancreatitis(OR=3.46,95%CI:1.19-10.87,P=0.023).PTBD was required in 16(14%)patients,and Bismuth type III or IV cholangiocarcinoma was a significant risk factor(OR=7.88,95%CI:1.33-155.0,P=0.010).Of 102 patients with initial unilateral drainage,49(48%)required bilateral *** sphincterotomy(OR=3.24,95%CI:1.27-8.78,P=0.004)and Bismuth II,III,or IV cholangiocarcinoma(OR=34.69,95%CI:4.88-736.7,P<0.001)were significant risk factors for bilateral ***:The endoscopic management of hilar cholangiocarcinoma is *** should be selected as a temporary drainage method because of its low risk of complications.

关键词： Hilar cholangiocarcinoma Endoscopic nasobiliary drainage Endoscopic biliary stenting Endoscopic sphincterotomy Complications