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217 results on '"Nishitani, T."'

1. Weakly Hyperbolic Systems by Symmetrization

Author

Colombini, F., Nishitani, T., and Rauch, J.

Subjects
Mathematics - Analysis of PDEs, 35L45, 35L40
Abstract

We study hyperbolic first order systems and propose a new method proving Gevrey well posedness, constructing a symmetrizer, motivated by a special Lyapunov function for linear ODE. The proof not only gives a priori estimates straightforward so simply but also clarifies some effects coming from the spectral structures other than the multiplicities of the eigenvalues.

Published
2015

2. Status of ITER neutron diagnostic development

Author

Krasilnikov, AV, Sasao, M, Kaschuck, Yu A, Nishitani, T, Batistoni, P, Zaveryaev, VS, Popovichev, S, Iguchi, T, Jarvis, ON, Källne, J, Fiore, CL, Roquemore, AL, Heidbrink, WW, Fisher, R, Gorini, G, Prosvirin, DV, Tsutskikh, A Yu, Donné, AJH, Costley, AE, and Walker, CI

Subjects
Atomic, Molecular, Nuclear, Particle and Plasma Physics, Fluids & Plasmas
Abstract

Due to the high neutron yield and the large plasma size many ITER plasma parameters such as fusion power, power density, ion temperature, fast ion energy and their spatial distributions in the plasma core can be measured well by various neutron diagnostics. Neutron diagnostic systems under consideration and development for ITER include radial and vertical neutron cameras (RNC and VNC), internal and external neutron flux monitors (NFMs), neutron activation systems and neutron spectrometers. The two-dimensional neutron source strength and spectral measurements can be provided by the combined RNC and VNC. The NFMs need to meet the ITER requirement of time-resolved measurements of the neutron source strength and can provide the signals necessary for real-time control of the ITER fusion power. Compact and high throughput neutron spectrometers are under development. A concept for the absolute calibration of neutron diagnostic systems is proposed. The development, testing in existing experiments and the engineering integration of all neutron diagnostic systems into ITER are in progress and the main results are presented. © 2005 IAEA, Vienna.

Published
2005

3. Overview of neutron and confined/escaping alpha diagnostics planned for ITER

Author

Sasao, M, Krasilnikov, AV, Nishitani, T, Batistoni, P, Zaveryaev, V, Kaschuck, Yu A, Popovichev, S, Iguchi, T, Jarvis, ON, Kallne, J, Fiore, CL, Roquemore, L, Heidbrink, WW, Donne, AJH, Costley, AE, and Walker, C

Subjects
Atomic, Molecular, Nuclear, Particle and Plasma Physics, Other Physical Sciences, Fluids & Plasmas
Abstract

Fusion product measurements planned for ITER are reviewed from the viewpoint of alpha particle-related physics studies. Recent advances in fusion plasma physics have extended the desirable measurement requirements to the megahertz region for neutron emission rate, better resolution of neutron profiles for the study of internal transport barriers (ITBs), etc. Employing threshold counters and/or scintillation detectors confers megahertz capability on neutron emission rate measurement. The changes in the neutron/alpha particle birth profile due to the formation of ITB and its deviation from uniformity on the magnetic flux surface can be measured by addition of eight viewing chords in an equatorial port plug and seven viewing chords from the divertor to the original radial neutron camera. On the other hand, it is still difficult to measure the distributions of confined and escaping alpha particles. Several proposals to resolve these difficulties are currently under investigation.

Published
2004

4. Plasma-surface interactions in TFTR DT experiments

Author

Owens, DK, Adler, H, Alling, P, Ancher, C, Anderson, H, Anderson, JL, Ashcroft, D, Barnes, Cris W, Barnes, G, Batha, S, Bell, MG, Bell, R, Bitter, M, Blanchard, W, Bretz, NL, Budny, R, Bush, CE, Camp, R, Caorlin, M, Cauffman, S, Chang, Z, Cheng, CZ, Collins, J, Coward, G, Darrow, DS, DeLooper, J, Duong, H, Dudek, L, Durst, R, Efthimion, PC, Ernst, D, Fisher, R, Fonck, RJ, Fredrickson, E, Fromm, N, Fu, GY, Furth, HP, Gentile, C, Gorelenkov, N, Grek, B, Grisham, LR, Hammett, G, Hanson, GR, Hawryluk, RJ, Heidbrink, W, Hermann, HW, Hill, KW, Hosea, J, Hsuan, H, Janos, A, Jassby, DL, Jobes, FC, Johnson, DW, Johnson, LC, Kamperschroer, J, Kugel, H, Lam, NT, LaMarche, PH, Loughlin, MJ, LeBlanc, B, Leonard, M, Levinton, FM, Machuzak, J, Mansfield, DK, Martin, A, Mazzucato, E, Majeski, R, Marmar, E, McChesney, J, McCormack, B, McCune, DC, McGuire, KM, McKee, G, Meade, DM, Medley, SS, Mikkelsen, DR, Mueller, D, Murakami, M, Nagy, A, Nazikian, R, Newman, R, Nishitani, T, Norris, M, O'Connor, T, Oldaker, M, Osakabe, M, Park, H, Park, W, Paul, SF, Pearson, G, Perry, E, Petrov, M, Phillips, CK, Pitcher, S, Raftopoulos, S, Ramsey, A, Rasmussen, DA, Redi, MH, Roberts, D, and Rogers, J

Subjects
Materials Engineering, Energy
Abstract

TFTR has begun its campaign to study deuterium-tritium fusion under reactor-like conditions. Variable amounts of deuterium and tritium neutral beam power have been used to maximize fusion power, study alpha heating, investigate alpha particle confinement, and search for alpha driven plasma instabilities. Additional areas of study include energy and particle transport and confinement, ICRF heating schemes for DT plasmas, tritium retention, and fusion in high βp plasmas. The majority of this work is done in the TFTR supershot confinement regime. To obtain supershots, extensive limiter conditioning using helium fueled ohmic discharges and lithium pellet injection into ohmic and neutral beam heated plasmas is performed, resulting in a low recycling limiter. The relationship between recycling and core plasma confinement has been studied by using helium, deuterium and high-Z gas puffs to simulate high recycling limiter conditions. These studies show that confinement in TFTR supershots is very sensitive to the influx of neutral particles at the plasma edge. © 1995, All rights reserved.

Published
1995

5. Confinement and heating of a deuterium-tritium plasma

Author

Hawryluk, RJ, Adler, H, Alling, P, Ancher, C, Anderson, H, Anderson, JL, Ashcroft, D, Barnes, Cris W, Barnes, G, Batha, S, Bell, MG, Bell, R, Bitter, M, Blanchard, W, Bretz, NL, Budny, R, Bush, CE, Camp, R, Caorlin, M, Cauffman, S, Chang, Z, Cheng, CZ, Collins, J, Coward, G, Darrow, DS, DeLooper, J, Duong, H, Dudek, L, Durst, R, Efthimion, PC, Ernst, D, Fisher, R, Fonck, RJ, Fredrickson, E, Fromm, N, Fu, GY, Furth, HP, Gentile, C, Gorelenkov, N, Grek, B, Grisham, LR, Hammett, G, Hanson, GR, Heidbrink, W, Herrmann, HW, Hill, KW, Hosea, J, Hsuan, H, Janos, A, Jassby, DL, Jobes, FC, Johnson, DW, Johnson, LC, Kamperschroer, J, Kugel, H, Lam, NT, LaMarche, PH, Loughlin, MJ, LeBlanc, B, Leonard, M, Levinton, FM, Machuzak, J, Mansfield, DK, Martin, A, Mazzucato, E, Majeski, R, Marmar, E, McChesney, J, McCormack, B, McCune, DC, McGuire, KM, McKee, G, Meade, DM, Medley, SS, Mikkelsen, DR, Mueller, D, Murakami, M, Nagy, A, Nazikian, R, Newman, R, Nishitani, T, Norris, M, O’Connor, T, Oldaker, M, Osakabe, M, Owens, DK, Park, H, Park, W, Paul, SF, Pearson, G, Perry, E, Petrov, M, Phillips, CK, Pitcher, S, Ramsey, A, Rasmussen, DA, Redi, MH, Roberts, D, Rogers, J, and Rossmassler, R

Subjects
Mathematical Sciences, Physical Sciences, Engineering, General Physics
Abstract

The Tomamak Fusion Test reactor has performed initial high-power experiments with the plasma fueled with nominally equal densities of deuterium and tritium. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by ∼20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by α particles created by the D-T fusion reactions. © 1994 The American Physical Society.

Published
1994

6. Fusion power production from TFTR plasmas fueled with deuterium and tritium

Author

Strachan, JD, Adler, H, Alling, P, Ancher, C, Anderson, H, Anderson, JL, Ashcroft, D, Barnes, Cris W, Barnes, G, Batha, S, Bell, MG, Bell, R, Bitter, M, Blanchard, W, Bretz, NL, Budny, R, Bush, CE, Camp, R, Caorlin, M, Cauffman, S, Chang, Z, Cheng, CZ, Collins, J, Coward, G, Darrow, DS, DeLooper, J, Duong, H, Dudek, L, Durst, R, Efthimion, PC, Ernst, D, Fisher, R, Fonck, RJ, Fredrickson, E, Fromm, N, Fu, GY, Furth, HP, Gentile, C, Gorelenkov, N, Grek, B, Grisham, LR, Hammett, G, Hanson, GR, Hawryluk, RJ, Heidbrink, W, Herrmann, HW, Hill, KW, Hosea, J, Hsuan, H, Janos, A, Jassby, DL, Jobes, FC, Johnson, DW, Johnson, LC, Kamperschroer, J, Kugel, H, Lam, NT, LaMarche, PH, Loughlin, MJ, LeBlanc, B, Leonard, M, Levinton, FM, Machuzak, J, Mansfield, DK, Martin, A, Mazzucato, E, Majeski, R, Marmar, E, McChesney, J, McCormack, B, McCune, DC, McGuire, KM, McKee, G, Meade, DM, Medley, SS, Mikkelsen, DR, Mueller, D, Murakami, M, Nagy, A, Nazikian, R, Newman, R, Nishitani, T, Norris, M, O’Connor, T, Oldaker, M, Osakabe, M, Owens, DK, Park, H, Park, W, Paul, SF, Pearson, G, Perry, E, Petrov, M, Phillips, CK, Pitcher, S, Ramsey, AT, Rasmussen, DA, Redi, MH, Roberts, D, and Rogers, J

Subjects
Neurodegenerative, Mathematical Sciences, Physical Sciences, Engineering, General Physics
Abstract

Peak fusion power production of 6.2±0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total power of 29.5 MW. These plasmas have an inferred central fusion alpha particle density of 1.2×1017 m-3 without the appearance of either disruptive magnetohydrodynamics events or detectable changes in Alfvén wave activity. The measured loss rate of energetic alpha particles agreed with the approximately 5% losses expected from alpha particles which are born on unconfined orbits. © 1994 The American Physical Society.

Published
1994

29. Development of 275kV gas cooled type gas-insulated power transformer

Author

Kudo, A., Nishitani, T., Yoshikawa, T., and Wan, C.T.

Subjects
Electric transformers -- Design and construction, Electric insulators -- Usage, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A world's first 275kV gas cooled type gas insulated power transformer with a low sound level ideal for urban area, which depends on SF6 gas alone for both insulation and cooling, was developed and has been put into commercial service since 1990 in Hong Kong. This paper presents the design philosophy, the principal technical items, the rating and the feature of 275kV 30MVA transformer, the performance test results, and the long term energization test result of the transformer.

Published
1993

40. Calibration experiments of [sup 3]He neutron detectors for analyzing neutron emissivity in the hot-ion mode on the GAMMA 10 tandem mirror

Author

Kohagura, J., Cho, T., Hirata, M., Watanabe, H., Minami, R., Numakura, T., Yoshida, M., Ito, H., Tatematsu, Y., Yatsu, K., Miyoshi, S., Ogura, K., Kondoh, T., Nishitani, T., Kwon, M., and England, A.C.

Abstract

Under the international fusion cooperating research, ³He neutron detectors in the GAMMA 10 tandem mirror are calibrated by the use of a [sup 252]Cf spontaneous fission neutron source (8.96 × 10[sup 4]n/s). The calibration experiments are carried out with a "rail system" placed along the magnetic axis of the GAMMA 10 central-cell region, where hot ions in the plasma experiments with the bulk temperatures of ∼10 keV are produced. As compared to a previous neutron monitoring system with a BF[sub 3] detector in GAMMA 10, the present ³He systems are designed with about two orders-of-magnitude higher neutron-counting efficiency for analyzing a neutron emissivity from the plasmas in a single plasma discharge alone. Two ³He systems are installed near the middle and the end of the central cell so as to identify the central-cell hot-ion axial profile. The filling pressure of ³He, the effective length, and the diameter of the detector are designed as 5 bar, 300 mm, and 50 mm, respectively. The detector output spectra are carefully analyzed by the use of a preamplifier, a shaping amplifier, as well as a multichannel analyzer for each ³He detector. In the present article, the neutron-counting data from the two ³He detectors due to the on-axis [sup 252]Cf scan are interpreted in terms of the d[sup -2] intensity dependence (d being the distance between the detector and the neutron source) as well as the effects of the central-cell magnetic coils and the other machine structural components.

Published
2003

46. Development of in-vessel components of the microfission chamber for ITER1

Author

Ishikawa, M., Kondoh, T., Ookawa, K., Fujita, K., Yamauchi, M., Hayakawa, A., Nishitani, T., and Kusama, Y.

Subjects
Fusion Products and Fast Ions—Ramon J. Leeper, Session Chairman
Abstract

Microfission chambers (MFCs) will measure the total neutron source strength in ITER. The MFCs will be installed behind blanket modules in the vacuum vessel (VV). Triaxial mineral insulated (MI) cables will carry signals from the MFCs. The joint connecting triaxial MI cables in the VV must be considered because the MFCs and the MI cables will be installed separately at different times. Vacuum tight triaxial connector of the MI cable has been designed and a prototype has been constructed. Performance tests indicate that the connector can be applied to the ITER environment. A small bending-radius test of the MI cable indicates no observed damage at a curvature radius of 100 mm.

Published
2010

47. 900-L liquid xenon cryogenic system operation for the MEG experiment

Author

Haruyama, T., Kasami, K., Mihara, S., Hisamatsu, Y., Iawamoto, W., Mori, T., Nishiguchi, H., Otani, W., Sawada, R., Yusuke Uchiyama, and Nishitani, T.

Subjects
Physics::Instrumentation and Detectors, Astrophysics::Instrumentation and Methods for Astrophysics, Detectors and Experimental Techniques
Abstract

A cryogenic system for the MEG (muon rare decay) experiment has started operation at the Paul Sherrer Institute in Zurich. The main part of the MEG detector is the 900-L liquid xenon calorimeter for gamma ray detection, equipped with 850 photo multipliers directly immersed in liquid xenon. A 200 W pulse tube cryocooler enabled LN2-free operation of this calorimeter. A liquid purification system; using a liquid pump and a zero boil-off 1000-L cryogenic buffer dewar is also included in the system. The first entire engineering run was carried out in November-December 2007 and satisfactory cryogenic performances were confirmed.

Published
2009

48. Overview of neutron and confined/escaping alpha diagnostics planned for ITER

Author

Sasao, M., Krasilnikov, A.V., Nishitani, T., Batistoni, P., Zaveryaev, V., Kaschuck, Y.A., Popovichev, S., Iguchi, T., Jarvis, O.N., Kallne, J., Fiore, C.L., Roquemore, L., Heidbrink, W.W., Donne, A.J. H., Costley, A.E., and Walker, C.

Subjects
Physics::Plasma Physics, Astrophysics::High Energy Astrophysical Phenomena
Abstract

Fusion product measurements planned for ITER are reviewed from the viewpoint of alpha particle-related physics studies. Recent advances in fusion plasma physics have extended the desirable measurement requirements to the megahertz region for neutron emission rate, better resolution of neutron profiles for the study of internal transport barriers (ITBs), etc. Employing threshold counters and/or scintillation detectors confers megahertz capability on neutron emission rate measurement. The changes in the neutron/alpha particle birth profile due to the formation of ITB and its deviation from uniformity on the magnetic flux surface can be measured by addition of eight viewing chords in an equatorial port plug and seven viewing chords from the divertor to the original radial neutron camera. On the other hand, it is still difficult to measure the distributions of confined and escaping alpha particles. Several proposals to resolve these difficulties are currently under investigation.

Published
2004

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