Pub Date : 2011-02-23DOI: 10.1017/S0263034611000887
H. Sakagami, Y. Kaseda, T. Taguchi, T. Johzaki
As the binary collision process requires much more computation time, a statistical electron-electron collision model based on modified Langevin equation is developed to reduce it. This collision model and a simple electron-ion scattering model are installed into one-dimensional PIC code, and collisional effects on fast electron generation and transport in fast ignition are investigated. In the collisional case, initially thermal electrons are heated up to a few hundred keV due to direct energy transfer by electron-electron collision, and they are also heated up to MeV by Joule heating induced by electron-ion scattering. Thus the number of low energy component of fast electrons increase than that in the collisionless case.
{"title":"Collisional Effects on Fast Electron Generation and Transport in Fast Ignition","authors":"H. Sakagami, Y. Kaseda, T. Taguchi, T. Johzaki","doi":"10.1017/S0263034611000887","DOIUrl":"https://doi.org/10.1017/S0263034611000887","url":null,"abstract":"As the binary collision process requires much more computation time, a statistical electron-electron collision model based on modified Langevin equation is developed to reduce it. This collision model and a simple electron-ion scattering model are installed into one-dimensional PIC code, and collisional effects on fast electron generation and transport in fast ignition are investigated. In the collisional case, initially thermal electrons are heated up to a few hundred keV due to direct energy transfer by electron-electron collision, and they are also heated up to MeV by Joule heating induced by electron-ion scattering. Thus the number of low energy component of fast electrons increase than that in the collisionless case.","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"110 1","pages":"405"},"PeriodicalIF":0.0,"publicationDate":"2011-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81454046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-02-23DOI: 10.1016/J.FUSENGDES.2004.01.002
T. Hino, Y. Yamauchi, S. Satoh, Y. Hirohata, A. Komori, A. Sagara, N. Noda, N. Ashikawa, S. Masuzaki, K. Nishimura, N. Ohyabu, O. Motojima
{"title":"Retention and Desorption of Hydrogen and Helium in Stainless Steel Wall","authors":"T. Hino, Y. Yamauchi, S. Satoh, Y. Hirohata, A. Komori, A. Sagara, N. Noda, N. Ashikawa, S. Masuzaki, K. Nishimura, N. Ohyabu, O. Motojima","doi":"10.1016/J.FUSENGDES.2004.01.002","DOIUrl":"https://doi.org/10.1016/J.FUSENGDES.2004.01.002","url":null,"abstract":"","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"1 1","pages":"76"},"PeriodicalIF":0.0,"publicationDate":"2011-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88585243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An access-control system has been developed for the safety operation of the large helical device(LHD)at the National Institute for Fusion Science.The central part of the control system consists of a main computer,a manual-operation box and a sequencer-control system.The system monitors five turnstiles,eight shielding doors and other points of entry and directly supplies the interlock signals to the LHD control system.The sequencer-control system,which provides independent access control of each gate,is effective to control simultaneously all of the entry according to the status of the LHD and to permit the access of radiation workers belonging to a specific work group according to the situation of LHD plasma experiment.The safety management of LHD experiments has been performed without any serious troubles by this access control system including the interlock system since 1998.
{"title":"Report of Operational Results of an Access Control System Developed for LHD Controlled Area","authors":"T. Kawano, Y. Narushima","doi":"10.12950/RSM2002.2.17","DOIUrl":"https://doi.org/10.12950/RSM2002.2.17","url":null,"abstract":"An access-control system has been developed for the safety operation of the large helical device(LHD)at the National Institute for Fusion Science.The central part of the control system consists of a main computer,a manual-operation box and a sequencer-control system.The system monitors five turnstiles,eight shielding doors and other points of entry and directly supplies the interlock signals to the LHD control system.The sequencer-control system,which provides independent access control of each gate,is effective to control simultaneously all of the entry according to the status of the LHD and to permit the access of radiation workers belonging to a specific work group according to the situation of LHD plasma experiment.The safety management of LHD experiments has been performed without any serious troubles by this access control system including the interlock system since 1998.","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"23 1","pages":"448"},"PeriodicalIF":0.0,"publicationDate":"2011-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73533143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Takahata, S. Moriuchi, K. Ooba, T. Mito, S. Imagawa
We present a fourteen-year data summary of the hydraulic characteristics of the large helical device (LHD) poloidal coils. The superconductors of the poloidal coils are cable-in-conduit conductors (CICC) cooled by circulated supercritical helium. The long-term operation of the LHD demonstrates that the initial hydraulic characteristics can be maintained without flow obstruction. Fine mesh filters installed at the inlet trapped impurities during cool-down of the coils, confirmed by monitoring the pressure drop of the filters. The filters have an important role in removing particles of impurities in the helium and maintaining the hydraulic characteristics of the coils.
{"title":"Long-term Monitoring of Hydraulic Characteristics of LHD Poloidal Coils","authors":"K. Takahata, S. Moriuchi, K. Ooba, T. Mito, S. Imagawa","doi":"10.1585/PFR.7.2405008","DOIUrl":"https://doi.org/10.1585/PFR.7.2405008","url":null,"abstract":"We present a fourteen-year data summary of the hydraulic characteristics of the large helical device (LHD) poloidal coils. The superconductors of the poloidal coils are cable-in-conduit conductors (CICC) cooled by circulated supercritical helium. The long-term operation of the LHD demonstrates that the initial hydraulic characteristics can be maintained without flow obstruction. Fine mesh filters installed at the inlet trapped impurities during cool-down of the coils, confirmed by monitoring the pressure drop of the filters. The filters have an important role in removing particles of impurities in the helium and maintaining the hydraulic characteristics of the coils.","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"18 1","pages":"95"},"PeriodicalIF":0.0,"publicationDate":"2011-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73481536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Murakami, H. Sakaue, D. Kato, S. Morita, N. Yamamoto, T. Watanabe
We measured extreme ultraviolet spectra of plasmas in the Large Helical Device after an Fe pellet was injected and analyzed the Fe XXI spectral lines λ 12.12 nm (2s22p2 3P2-2s2p3 3P2) and λ 12.875 nm (2s22p2 3P0-2s2p3 3D1). By constructing a collisional-radiative model for Fe XXI, we obtained the electron density dependence of the line intensity ratio, which is the result of the excitation process among the fine-structure levels of the ground state, 2s22p2 3PJ by electron and proton impact. Using the obtained electron density dependence, we estimated the electron density from the measured intensity ratio. By comparing the estimated density with the electron density distribution measured by a far infrared interferometer, we could estimate the location of the Fe XXI emitting region. We found that Fe XXI appeared first around the density peak formed by the pellet and later expanded toward a low-density region. The corresponding electron temperature of the location is lower than that for ionization equilibrium, and the Fe XXI ions are expected to be in a non-equilibrium ionization state.
{"title":"Analysis of Fe XXI Spectral Lines Measured in LHD Plasmas","authors":"I. Murakami, H. Sakaue, D. Kato, S. Morita, N. Yamamoto, T. Watanabe","doi":"10.1585/PFR.5.S2021","DOIUrl":"https://doi.org/10.1585/PFR.5.S2021","url":null,"abstract":"We measured extreme ultraviolet spectra of plasmas in the Large Helical Device after an Fe pellet was injected and analyzed the Fe XXI spectral lines λ 12.12 nm (2s22p2 3P2-2s2p3 3P2) and λ 12.875 nm (2s22p2 3P0-2s2p3 3D1). By constructing a collisional-radiative model for Fe XXI, we obtained the electron density dependence of the line intensity ratio, which is the result of the excitation process among the fine-structure levels of the ground state, 2s22p2 3PJ by electron and proton impact. Using the obtained electron density dependence, we estimated the electron density from the measured intensity ratio. By comparing the estimated density with the electron density distribution measured by a far infrared interferometer, we could estimate the location of the Fe XXI emitting region. We found that Fe XXI appeared first around the density peak formed by the pellet and later expanded toward a low-density region. The corresponding electron temperature of the location is lower than that for ionization equilibrium, and the Fe XXI ions are expected to be in a non-equilibrium ionization state.","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"1 1","pages":"422"},"PeriodicalIF":0.0,"publicationDate":"2010-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90101194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Maeyama, A. Ishizawa, Tomoyasu Watanabe, M. Koric, N. Nakajima, S. Tsuji-Iio, H. Tsutsui
Effects of time-varying sheared E×B flow on turbulence driven by slab ion temperature gradient instabilities are investigated by means of Landau fluid simulation. Here, the E×B flow, which consists of stationary and time-periodic oscillatory parts, is externally imposed to the turbulence. The dependence on the amplitude and frequency of E×B flow is examined in the case that the amplitude of oscillatory part is the same or less than that of stationary part. The ion heat transport caused by turbulence oscillates with the same period as the E×B flow and the time-averaged transport coefficient is larger than the coefficient which is evaluated without the oscillatory part. The time-averaged coefficient is maximized when the amplitude of oscillatory part is equal to that of stationary part. As the frequency of E×B flow increases, the time-averaged coefficient decreases and is close to the coefficient which is evaluated without the oscillatory part. This mechanism is explained by introducing a kind of the logist...
{"title":"Effects of Time-varying E×B Flow on Slab Ion-temperature-gradient Turbulence","authors":"S. Maeyama, A. Ishizawa, Tomoyasu Watanabe, M. Koric, N. Nakajima, S. Tsuji-Iio, H. Tsutsui","doi":"10.1063/1.3432121","DOIUrl":"https://doi.org/10.1063/1.3432121","url":null,"abstract":"Effects of time-varying sheared E×B flow on turbulence driven by slab ion temperature gradient instabilities are investigated by means of Landau fluid simulation. Here, the E×B flow, which consists of stationary and time-periodic oscillatory parts, is externally imposed to the turbulence. The dependence on the amplitude and frequency of E×B flow is examined in the case that the amplitude of oscillatory part is the same or less than that of stationary part. The ion heat transport caused by turbulence oscillates with the same period as the E×B flow and the time-averaged transport coefficient is larger than the coefficient which is evaluated without the oscillatory part. The time-averaged coefficient is maximized when the amplitude of oscillatory part is equal to that of stationary part. As the frequency of E×B flow increases, the time-averaged coefficient decreases and is close to the coefficient which is evaluated without the oscillatory part. This mechanism is explained by introducing a kind of the logist...","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"10 18 1","pages":"324"},"PeriodicalIF":0.0,"publicationDate":"2010-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82876868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Takahashi, T. Shimozuma, M. Yokoyama, T. Ido, S. Kubo, A. Shimizu, Y. Yoshimura, H. Igami, T. Mutoh
We have investigated the transition to Core Electron‐Root Confinement (CERC) using the 77 GHz ECRH system, which was newly installed in the Large Helical Device (LHD). The focal point scan of the ECRH was carried out shot by shot in the same poloidal surface along the magnetic field of 2.75 T, which is the fundamental resonance surface for 77 GHz ECRH. The formation of the steep gradient in the electron temperature and the change of the radial electric field from negative to positive value in the plasma core region were observed by the ECRH injection to ρ<0.5. The foot point of the peaked profile of the electron temperature appeared near the m/n = 2/1 rational surface, which was located at ρ∼0.5. These results imply that localized ECRH in the inner region within the lower order rational surface and/or the electron heat flux across the rational surface play important roles for the transition to CERC. We also confirmed that the calculated radial electric field from a neoclassical theory qualitatively agreed...
{"title":"Study of CERC Using Newly Installed 77 GHz Gyrotron in LHD","authors":"H. Takahashi, T. Shimozuma, M. Yokoyama, T. Ido, S. Kubo, A. Shimizu, Y. Yoshimura, H. Igami, T. Mutoh","doi":"10.1063/1.3273798","DOIUrl":"https://doi.org/10.1063/1.3273798","url":null,"abstract":"We have investigated the transition to Core Electron‐Root Confinement (CERC) using the 77 GHz ECRH system, which was newly installed in the Large Helical Device (LHD). The focal point scan of the ECRH was carried out shot by shot in the same poloidal surface along the magnetic field of 2.75 T, which is the fundamental resonance surface for 77 GHz ECRH. The formation of the steep gradient in the electron temperature and the change of the radial electric field from negative to positive value in the plasma core region were observed by the ECRH injection to ρ<0.5. The foot point of the peaked profile of the electron temperature appeared near the m/n = 2/1 rational surface, which was located at ρ∼0.5. These results imply that localized ECRH in the inner region within the lower order rational surface and/or the electron heat flux across the rational surface play important roles for the transition to CERC. We also confirmed that the calculated radial electric field from a neoclassical theory qualitatively agreed...","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"6 3 1","pages":"31"},"PeriodicalIF":0.0,"publicationDate":"2009-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78311959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Oka, L. Grisham, N. Umeda, K. Ikeda, Y. Takeiri, K. Tsumori, A. Honda, Y. Ikeda, O. Kaneko, K. Nagaoka, M. Osakabe, T. Yamamoto, E. Asano, T. Kondo, M. Sato, M. Shibuya
The velocity spectra of the negative-ion-(H−) based neutral beams are studied in high-performance large-area ion sources during injection into large helical device fusion plasmas. We are conducting systematic observations in standard neutral beam injection to correlate beam spectra with source operating conditions. Almost all of the transmitted beam power was at full acceleration energy (∼170keV). The small stripping beam component which was produced in the extraction gap was evaluated to be about 9%–22% by amplitude of the measured spectra for the sources in beam lines 1 and 2. H− production uniformity from the spectrum profile was 86%–90% for three sources. For the longest pulse injection during 74 and 128 s, a full energy component tended to decrease with time, while the accelerator gap stripping tail tended to increase slightly with time, which is attributed to beam-induced outgassing in the accelerator. A higher conductance multislot ground grid accelerator appeared to show little growth in the accel...
{"title":"Doppler Shift Spectra of Hα Lines from Negative Ion Based Neutral Beams","authors":"Y. Oka, L. Grisham, N. Umeda, K. Ikeda, Y. Takeiri, K. Tsumori, A. Honda, Y. Ikeda, O. Kaneko, K. Nagaoka, M. Osakabe, T. Yamamoto, E. Asano, T. Kondo, M. Sato, M. Shibuya","doi":"10.1063/1.2166676","DOIUrl":"https://doi.org/10.1063/1.2166676","url":null,"abstract":"The velocity spectra of the negative-ion-(H−) based neutral beams are studied in high-performance large-area ion sources during injection into large helical device fusion plasmas. We are conducting systematic observations in standard neutral beam injection to correlate beam spectra with source operating conditions. Almost all of the transmitted beam power was at full acceleration energy (∼170keV). The small stripping beam component which was produced in the extraction gap was evaluated to be about 9%–22% by amplitude of the measured spectra for the sources in beam lines 1 and 2. H− production uniformity from the spectrum profile was 86%–90% for three sources. For the longest pulse injection during 74 and 128 s, a full energy component tended to decrease with time, while the accelerator gap stripping tail tended to increase slightly with time, which is attributed to beam-induced outgassing in the accelerator. A higher conductance multislot ground grid accelerator appeared to show little growth in the accel...","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"48 1","pages":"73"},"PeriodicalIF":0.0,"publicationDate":"2006-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74203503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"INTERACTION BETWEEN A COLUMNAR VORTEX AND EXTERNAL TURBULENCE","authors":"N. Takahashi, T. Miyazaki","doi":"10.1007/1-4020-4181-0_4","DOIUrl":"https://doi.org/10.1007/1-4020-4181-0_4","url":null,"abstract":"","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"5 1","pages":"31-38"},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73584140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Yakovlev, S. Inagaki, T. Shimozuma, S. Kubo, T. Morisaki, Y. Nagayama, K. Kawahata, A. Komori
Core electron temperature profile flattening is observed in a large helical device [A. Iiyoshi et al. Nucl. Fusion 39, 1245 (1999)] inward shifted plasma with counter-neutral beam injection. To study this phenomenon, heat pulse experiments are performed by on-axis electron cyclotron heating power modulation. A unique feature of heat pulse propagation is observed near the m∕n=2∕1 rational surface (m, n are the poloidal and toroidal mode numbers, respectively). A simultaneous response of the temperature perturbation on radially separated flux surfaces is shown. The change in the magnetic field topology due to the presence of a magnetic island structure can explain this nonmonotonic heat pulse propagation. The estimated O-point position of the island is located near the m∕n=2∕1 rational surface.
{"title":"Heat Pulse Propagation across the Rational Surface in Large Helical Device Plasma with Counter Neutral Beam Injection","authors":"M. Yakovlev, S. Inagaki, T. Shimozuma, S. Kubo, T. Morisaki, Y. Nagayama, K. Kawahata, A. Komori","doi":"10.1063/1.2044447","DOIUrl":"https://doi.org/10.1063/1.2044447","url":null,"abstract":"Core electron temperature profile flattening is observed in a large helical device [A. Iiyoshi et al. Nucl. Fusion 39, 1245 (1999)] inward shifted plasma with counter-neutral beam injection. To study this phenomenon, heat pulse experiments are performed by on-axis electron cyclotron heating power modulation. A unique feature of heat pulse propagation is observed near the m∕n=2∕1 rational surface (m, n are the poloidal and toroidal mode numbers, respectively). A simultaneous response of the temperature perturbation on radially separated flux surfaces is shown. The change in the magnetic field topology due to the presence of a magnetic island structure can explain this nonmonotonic heat pulse propagation. The estimated O-point position of the island is located near the m∕n=2∕1 rational surface.","PeriodicalId":7974,"journal":{"name":"Annual Report of National Institute for Fusion Science","volume":"69 3 1","pages":"15"},"PeriodicalIF":0.0,"publicationDate":"2005-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90252436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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