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Journal Articles

Summary results of subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))"

Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.

Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08

JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.

Journal Articles

Dating of buried wood logs and fragments for high resolution reconstruction of landslide histories; Case studies in the Japanese Alps region in the historical times

Yamada, Ryuji*; Kimura, Takashi*; Kariya, Yoshihiko*; Sano, Masaki*; Tsushima, Akane*; Li, Z.*; Nakatsuka, Takeshi*; Kokubu, Yoko; Inoue, Kimio*

Sabo Gakkai-Shi, 73(5), p.3 - 14, 2021/01

We discuss the applicability of dating methods for determining landslide chronologies in relation to the type of samples and the sampling location. Case studies are carried out with fossil wood samples buried in the colluvial soil of large-scale landslides occurred in two areas of the Japanese Alps region. Ages are determined by accelerator mass spectrometry radiocarbon dating and dendrochronological analysis using the oxygen isotope composition of tree ring cellulose. Most of ages for Dondokosawa rock avalanche are concordant with the period of AD 887 Ninna (Goki-Shichido) earthquake. Ages for Ohtsukigawa debris avalanche are not concentrated in a specific period. In order to obtain accurate age of large-scale landslide, utilizing buried large diameter tree trunk or branches with the good preservation condition has a lot of advantages because it allows us to compare the landslide chronology with historical records of heavy rainfall and large earthquakes.

Journal Articles

Seawater immersion tests of irradiated Zircaloy-2 cladding tube

Sekio, Yoshihiro; Yamagata, Ichiro; Yamashita, Shinichiro; Inoue, Masaki; Maeda, Koji

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 10 Pages, 2014/10

In the Fukushima Dai-ichi Nuclear Power Plant accident, seawater was temporarily injected into the spent fuel pools since water cooling and feeding functions were lost. For fuel assemblies which experienced seawater immersion, surface corrosion due to seawater constituents and the resultant degradation of mechanical property are of concern. Therefore, in order to assess the integrity of fuel assemblies (especially cladding tubes), the effects of seawater immersion on corrosion behavior and mechanical properties for as-recieved and irradiated Zircaloy-2 cladding tubes were investigated in the present study. As a result, no obvious surface corrosion and no significant degradation in the tensile strength property were observed after both artificial and natural seawater immersion tests for both steels. This suggests that the effects of seawater immersions on corrosion behavior and mechanical property (especially tensile property) for Zircaloy-2 cladding tubes are probably negligible.

JAEA Reports

Temperature and chemical history for spent fuel pools in Fukushima Dai-ichi Nuclear Power Station; Units 1 through 4

Inoue, Masaki; Asaka, Takeo

JAEA-Review 2014-020, 46 Pages, 2014/06

JAEA-Review-2014-020.pdf:5.81MB

Integrity of fuel assemblies (FAs) stored in the spent fuel pools (SFPs) of Fukushima Dai-ichi Nuclear Power Station (units 1 through 4) is one of the most important issues to transport the FAs to the common pool for long term storage. The SFPs had lost their functions of decay heat removal and water supply due to the station blackout. Since fresh and sea waters were injected into and concrete fragments by hydrogen explosions fell into the SFPs, the FAs have been exposed to much more corrosive environments than usual ones. In this report, many events during the accidents were investigated from a view point of temperature and chemical constituents in the SFPs in order to evaluate integrity for fuel assemblies during long term storage in the common pool by means of corrosion tests.

Journal Articles

Structural and functional characterization of the ${it Geobacillus}$ copper nitrite reductase; Involvement of the unique N-terminal region in the interprotein electron transfer with its redox partner

Fukuda, Yota*; Koteishi, Hiroyasu*; Yoneda, Ryohei*; Tamada, Taro; Takami, Hideto*; Inoue, Tsuyoshi*; Nojiri, Masaki

Biochimica et Biophysica Acta; Bioenergetics, 1837(3), p.396 - 405, 2014/03

 Times Cited Count:12 Percentile:43.65(Biochemistry & Molecular Biology)

The crystal structures of copper-containing nitrite reductase (CuNiR) from the thermophilic Gram-positive bacterium ${it Geobacillus kaustophilus}$ HTA426 and the amino (N)-terminal 68 residue-deleted mutant were determined at resolutions of 1.3${AA}$ and 1.8${AA}$, respectively. Both structures show a striking resemblance with the overall structure of the well-known CuNiRs composed of two Greek key $$beta$$-barrel domains; however, a remarkable structural difference was found in the N-terminal region. The unique region has one $$beta$$-strand and one $$alpha$$-helix extended to the northern surface of the type-1 copper site. The superposition of the ${it Geobacillus}$ CuNiR model on the electron-transfer complex structure of CuNiR with the redox partner cytochrome ${it c$_{551}$}$ in other denitrifier system led us to infer that this region contributes to the transient binding with the partner protein during the interprotein electron transfer reaction in the ${it Geobacillus}$ system. Furthermore, electron-transfer kinetics experiments using N-terminal residue-deleted mutant and the redox partner, ${it Geobacillus}$ cytochrome ${it c$_{551}$}$, were carried out. These structural and kinetics studies demonstrate that that region is directly involved in the specific partner recognition.

Journal Articles

Long-pulse beam acceleration of MeV-class H$$^{-}$$ ion beams for ITER NB accelerator

Umeda, Naotaka; Kashiwagi, Mieko; Taniguchi, Masaki; Tobari, Hiroyuki; Watanabe, Kazuhiro; Dairaku, Masayuki; Yamanaka, Haruhiko; Inoue, Takashi; Kojima, Atsushi; Hanada, Masaya

Review of Scientific Instruments, 85(2), p.02B304_1 - 02B304_3, 2014/02

 Times Cited Count:10 Percentile:49.27(Instruments & Instrumentation)

In order to realize neutral beam systems in ITER whose target is to produce D$$^{-}$$ ion beam of 1 MeV, 200 A/m$$^{2}$$ during 3600s, the electrostatic five-stages negative ion accelerator has been developed at JAEA. To extend pulse length, heat load of the acceleration grids was reduced by controlling the ion beam trajectory. Namely, the beam deflection due to the residual magnetic filter in the accelerator was suppressed with the newly developed extractor with a 0.5 mm off-set aperture displacement. The use of new extractor improved the deflection angle from 6 mrad to 1 mrad, resulting in the reduction of direct interception of negative ions from 23% to 15% of the total acceleration power, respectively. As a result, the pulse length of 130 A/m$$^{2}$$, 881 keV H$$^{-}$$ ion beam has been successfully extended from a previous value of 0.4s to 8.7s.

Journal Articles

Development of negative ion extractor in the high-power and long-pulse negative ion source for fusion application

Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Kojima, Atsushi; Yoshida, Masafumi; Taniguchi, Masaki; Dairaku, Masayuki; Maejima, Tetsuya; Yamanaka, Haruhiko; Watanabe, Kazuhiro; et al.

Review of Scientific Instruments, 85(2), p.02B320_1 - 02B320_3, 2014/02

 Times Cited Count:24 Percentile:76.32(Instruments & Instrumentation)

The negative ion extractor for high power and long-pulse operations is newly developed toward the neutral beam injector (NBI) for heating & current drive of future fusion machines such as ITER, JT-60 Super Advanced (SA) and DEMO reactor. The satisfactory cooling capability is designed in the thermal analysis. A negative ion production and a suppression of electrons are experimentally validated for this new extractor. As the results, the negative ion current shows increases by a factor of 1.3 with suppressing the electron current. The beam divergence angle is also maintained small enough, 4 mrad.

JAEA Reports

Long term performance of radial shielding subassemblies with zirconium hydride in sodium cooled fast reactor core; Hydrogen release into primary coolant and helium production in cladding tube steels

Inoue, Masaki; Kaito, Takeji

JAEA-Research 2013-041, 69 Pages, 2014/01

JAEA-Research-2013-041.pdf:4.61MB

Long term performance of radial shielding subassemblies with zirconium hydride, which is one of the key technologies to reduce reactor vessel radius, was evaluated for the demonstration fast breeder reactor core. Hydrogen permeation through cladding tube wall and release into primary coolant is essential to design cold traps and shielding performance. Also, higher thermal neutron fluence produces larger helium in cladding tube steels, and may degrade mechanical properties and dimensional stability. A new model was established to quantitatively calculate hydrogen release and helium production under steep gradient of neutron and $$gamma$$ ray fluxes in outer core region. Austenitic stainless steel (PNC316) and ferritic/martensitic steel (PNC-FMS) will not be capable for 60 years because of large helium production and high permeability, respectively. In contrast, dual wall tube combining PNC-FMS with surface oxidized Fe-18Cr-2Al alloy will be applicable for 60 years in case that manufacturing process is successfully developed.

JAEA Reports

Immersion test in artificial water and evaluation of strength property on fuel cladding tubes irradiated in Fugen Nuclear Power Plant

Yamagata, Ichiro; Hayashi, Takehiro; Mashiko, Shinichi*; Sasaki, Shinji; Inoue, Masaki; Yamashita, Shinichiro; Maeda, Koji

JAEA-Testing 2013-004, 23 Pages, 2013/11

JAEA-Testing-2013-004.pdf:8.59MB

In the accident of the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Co. accompanying the Great East Japan Earthquake, fuel assemblies kept in the spent fuel pool of reactor units 1-4, were exposed to the inconceivable environment such as falling and mixing of rubble, especially seawater were injected into unit 2-4. In order to evaluate the integrity of the fuel assemblies in spent fuel pools, and in the long-term storage after transported to the common storage pool, the immersion tests were performed using zircaloy-2 fuel cladding tubes irradiated in the advanced thermal reactor Fugen. The immersion liquid was prepared with doubling dilution of artificial seawater, which temperature was 80 $$^{circ}$$C and immersion time was about 336 hours, as assuming the situation of the pool. The results indicated zircaloy-2 cladding tubes had no significant corrosion and no influence on mechanical property by immersion tests with artificial seawater conditions of this work.

JAEA Reports

Dissolutions of oxide dispersion strengthened ferritic steels in various nitric acid solutions, 2; The Amount of the corrosion products in the dissolution process

Inoue, Masaki; Suto, Mitsuo; Koyama, Shinichi; Otsuka, Satoshi; Kaito, Takeji

JAEA-Research 2013-009, 78 Pages, 2013/10

JAEA-Research-2013-009.pdf:3.75MB

In order to exammine the applicability for advanced aqueous reprocessing system, the martensitic oxide dispersion strengthened ferritic steel (9Cr-ODS steel), which is the primary candidate material for high burnup fuel pin cladding tube in fast reactor cycle, was evaluated for the amount of corrosion products in the dissolution process. The quantity of corrosion products was calculated to investigate the influence of both various chemical processes and waste glass (vitrified high level radioactive wastes) by use of the results of a maximum cladding temperature fuel subassembly and the sum of all fuel subassemblies, respectively. The experimental results of immersion tests in flowing liquid sodium loops and fuel pin irradiation tests in fast reactors were reviewed to consider the effect of outer and inner corrosions in high burnup fuel pins on corrosion products. This work revealed that the sum of corrosion products depends largely on the mass transfer behavior in flowing liquid sodium.

Journal Articles

Structural analyses of HV bushing for ITER heating NB system

Tobari, Hiroyuki; Inoue, Takashi; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Dairaku, Masayuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Sakamoto, Keishi; Kuriyama, Masaaki*; et al.

Fusion Engineering and Design, 88(6-8), p.975 - 979, 2013/10

 Times Cited Count:1 Percentile:12.53(Nuclear Science & Technology)

The HV bushing, one of the ITER NB components, which is to be procured by JADA, is a multi-conductor feed through composed of five-stage double-layered insulator columns with large brazed ceramic ring and fiber reinforced plastic (FRP) ring. The HV bushing is a bulk head between insulation gas at 0.6 MPa and vacuum. The FRP ring is required to sustain the pressure load, seismic load and dead weight. Brazing area of the ceramic ring with Kovar is required to maintain vacuum leak tightness and pressure tightness against the air filled at 0.6 MPa. To design the HV bushing satisfying the safety factor of $$geq$$ 3.5, mechanical analyses were carried out. As for the FRP ring, it was confirmed that isotropic fiber cloth FRP rings should be used for sufficient strength against shear stress. Also, shape and fixation area of the Kovar sleeve were modified to lower the stress at the joint area. As a result, a design of the insulator for the HV bushing was established satisfying the requirement.

Journal Articles

Long-pulse production of the negative ion beams for JT-60SA

Kojima, Atsushi; Hanada, Masaya; Yoshida, Masafumi; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Grisham, L. R.*; et al.

Fusion Engineering and Design, 88(6-8), p.918 - 921, 2013/10

 Times Cited Count:6 Percentile:49.64(Nuclear Science & Technology)

In this paper, the recent activities are reported toward demonstration of the long pulse production. As for the improvement of uniform beam current profile, a symmetric magnetic field configuration for the source plasma production, a so-called tent-shaped filter, was found to be effective to improve the uniformity of the beam current profile. A similar configuration is applied to the JT-60 negative ion source whose plasma size is 1220 mm $$times$$ 564 mm. An estimation from trajectory calculations of primary electrons with the symmetric magnetic field configuration showed that the primary electrons were distributed uniformly in a longitudinal direction. As for the temperature control of the plasma grid, a prototype of the grid with cooling/heating by circulating a high-temperature fluorinated fluid has been developed. This grid was found to have a capability to control the temperature with a time constant of 10 s by considering the physical properties of the fluid.

Journal Articles

High temperature reaction tests between high-Cr ODS ferritic steels and U-Zr metallic fuel

Otsuka, Satoshi; Kaito, Takeji; Ukai, Shigeharu*; Inoue, Masaki; Okuda, Takanari*; Kimura, Akihiko*

Journal of Nuclear Materials, 441(1-3), p.286 - 292, 2013/10

 Times Cited Count:4 Percentile:37.15(Materials Science, Multidisciplinary)

The Al addition to ODS ferritic steels considerably improves the compatibility between U-Zr fuel and the ODS steels. The threshold temperature for reaction layer formation is roughly 50K higher in the Al-containing ODS ferritic steels than in those same steels without Al addition. The activity calculation results obtained using general thermodynamic data indicate the possibility that stabilization of the intact alpha-Zr layer by Al addition is the main mechanism for the compatibility improvement by Al addition.

Journal Articles

ODS cladding fuel pins irradiation tests using the BOR-60 reactor

Kaito, Takeji; Yano, Yasuhide; Otsuka, Satoshi; Inoue, Masaki; Tanaka, Kenya; Fedoseev, A. E.*; Povstyanko, A. V.*; Novoselov, A.*

Journal of Nuclear Science and Technology, 50(4), p.387 - 399, 2013/04

 Times Cited Count:9 Percentile:63.75(Nuclear Science & Technology)

In order to confirm the irradiation behavior of ODS steels and thus judge their applicability to fuel claddings, fuel pin irradiation tests using 9Cr and 12Cr-ODS claddings developed by JAEA were conducted to burnup of 11.9 at% and neutron dose of 51 dpa in the BOR-60. Superior properties of the ODS claddings concerning FCCI, dimensional stability under irradiation and so on were confirmed indicating good application prospects for high burnup fuel. On the other hand, peculiar irradiation behaviors, fuel pin failure and the microstructure change containing coarse and irregular precipitates, occurred in a part of the fuel pin with 9Cr-ODS cladding. This paper describes evaluation of the obtained irradiation data and the investigation results into the cause of the peculiar irradiation behaviors.

Journal Articles

Compensations of beamlet deflections for 1 MeV accelerator of ITER NBI

Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; Dairaku, Masayuki; Tobari, Hiroyuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Inoue, Takashi; DeEsch, H. P. L.*; Grisham, L. R.*; et al.

AIP Conference Proceedings 1515, p.227 - 236, 2013/02

 Times Cited Count:9 Percentile:94.55

In a five stage multi-aperture multi-grid (MAMuG) accelerator for the ITER neutral beam injector (NBI), 1 MeV, 40 A D$$^-$$ ion beam is required for 1 hour. However, beamlets are deflected due to (1) magnetic field for electron suppression and (2) space charge repulsion between beamlets, and consequently, cause excess grid heat load. A three dimensional beam analysis has been carried out to compensate the beamlet deflections. This paper shows that the beamlet deflections due to (1) and (2) are compensated by an aperture offset of only 0.6 mm applied to the aperture of 17 mm in diameter in the extractor and by a metal bar attached around aperture area beneath the extractor, respectively. When the metal bar is increased to 3 mm in thickness and installed 30 mm away from the aperture area, the beamlet is steered gently by the weaker electric field distortion. The beam optics was confirmed not deteriorated by those compensations. The presentation also discusses application of these compensation techniques to the ITER design.

Journal Articles

Analysis of electron temperature distribution by kinetic modeling of electron energy distribution function in JAEA 10 ampere negative ion source

Shibata, Takanori; Terasaki, Ryo*; Kashiwagi, Mieko; Inoue, Takashi; Dairaku, Masayuki; Taniguchi, Masaki; Tobari, Hiroyuki; Umeda, Naotaka; Watanabe, Kazuhiro; Sakamoto, Keishi; et al.

AIP Conference Proceedings 1515, p.177 - 186, 2013/02

 Times Cited Count:8 Percentile:94.55

In the neutral beam injector in JT-60SA, one of issues is that negative ion beam is partially intercepted at acceleration grids due to a spatial non-uniformity of negative ion production on large extraction area (0.9$$times$$0.45m$$^{2}$$). Previous experiments showed that fast electrons emitted from filament cathodes are transported in a longitudinal direction by $$mathbf{B} times textrm{grad} mathbf{B}$$ drift and the spatial distribution of electron temperature ($$T_e$$) strongly relates with the non-uniformity. In this study, a three-dimensional electron transport analysis has been developed. Electron temperature in the analysis agreed well with measurements in JAEA 10A ion source. This study clarified that the bias of $$T_e$$ distribution are caused by the following reasons; (1) fast electrons drifted in the longitudinal direction survives near the end wall with energy up to $$E$$ = 25-60 eV and (2) they produces thermal electrons by collision with plasma particles there.

Journal Articles

Vacuum insulation and achievement of 980 keV, 185 A/m$$^{2}$$ H$$^{-}$$ ion beam acceleration at JAEA for the ITER neutral beam injector

Tobari, Hiroyuki; Taniguchi, Masaki; Kashiwagi, Mieko; Dairaku, Masayuki; Umeda, Naotaka; Yamanaka, Haruhiko; Tsuchida, Kazuki; Takemoto, Jumpei; Watanabe, Kazuhiro; Inoue, Takashi; et al.

Plasma Science and Technology, 15(2), p.179 - 183, 2013/02

 Times Cited Count:1 Percentile:5.25(Physics, Fluids & Plasmas)

Vacuum insulation is a common issue for the accelerator and the HV bushing for the ITER NBI. The HV bushing has five-stage structure and each stage consists of double-layered insulators. Hence, several triple points exist around the insulators. To reduce electric field at those points simultaneously, three types of stress ring were developed. In voltage holding test of a full-scale mockup equipped with those stress rings, 120% of rated voltage was sustained and the voltage holding capability required in ITER was verified. In the MeV accelerator, voltage holding capability was not sufficient due to breakdown triggered by electric field concentration at edge and corner on grid components. By extending gap length, 1 MV was sustained in vacuum. Furthermore, with new accelerator grids which compensates beam deflection due to magnetic field and space charge repulsion between beamlets, 980 keV, 185 A/m$$^{2}$$ H$$^{-}$$ ion beam acceleration was demonstrated, which was close to ITER requirement.

Journal Articles

Seven cysteine-deficient mutants depict the interplay between thermal and chemical stabilities of individual cysteine residues in mitogen-activated protein kinase c-Jun N-terminal kinase 1

Nakaniwa, Tetsuko*; Fukata, Harumi*; Inoue, Tatsuya*; Goda, Masaki*; Nakai, Ryoko*; Kirii, Yasuyuki*; Adachi, Motoyasu; Tamada, Taro; Segawa, Shinichi*; Kuroki, Ryota; et al.

Biochemistry, 51(42), p.8410 - 8421, 2012/10

 Times Cited Count:14 Percentile:39.86(Biochemistry & Molecular Biology)

Protein kinase is a vital drug target for the treatment of a wide range of diseases. To investigate the effect of cysteine mutation on the function, stability and structure of kinase, free cysteines of c-Jun N-terminal kinase 1 (JNK1) were systematically removed by mutation. Two cysteine-destructed mutants in which three (M3) and seven (M7) cysteine residues are removed, yielded about 5 and 2 times than wild type JNK-1 (M0). SDS PAGE analysis showed that the aggregation was less in the case of M3 and M7. Thermal unfolding experiment of M0, M3 and M7 using by differential scanning calorimetry proceeded at least three state unfolding. Crystal structure of the M3 mutant was determined to 2.6 ${AA}$ resolution, which was identical to that of the wild-type. Consequently, due to the highest yield, its improved stability against aggregation and its structural similarity to the wild type, the M3 mutant is suitable for the use of further characterization of its function and structure.

JAEA Reports

Dissolutions of oxide dispersion strengthened ferritic steels in various nitric acid solutions; Martensitic 9Cr-ODS steels

Inoue, Masaki; Ikeuchi, Hirotomo; Takeuchi, Masayuki; Koyama, Shinichi; Suto, Mitsuo

JAEA-Research 2011-057, 100 Pages, 2012/03

JAEA-Research-2011-057.pdf:3.23MB

Corrosion resistance of fuel pin cladding tube materials is one of the most important properties to design aqueous reprocessing process. The martensitic oxide dispersion strengthened ferritic steel, names as "9Cr-ODS" steel, is the primary candidate of high burnup fuel pin cladding tube for fast reactor cycle. Because 9Cr-ODS steel contains lower chromium than stainless steels, oxidizing species in nitric acid medium needs to reduce its corrosion rate. In spent fuel dissolvers, although both nitric acid and metallic ions concentrations change, corrosion potential of 9Cr-ODS steel tends to increase gradually and stabilize protective passive layer effectively.

Journal Articles

Vacuum insulation of the high energy negative ion source for fusion application

Kojima, Atsushi; Hanada, Masaya; Hilmi, A.*; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Kobayashi, Shinichi*; et al.

Review of Scientific Instruments, 83(2), p.02B117_1 - 02B117_5, 2012/02

 Times Cited Count:14 Percentile:59.32(Instruments & Instrumentation)

Production of 500 keV, 3 A beams has been successfully achieved in the JT-60 negative by overcoming the low voltage holding of the accelerator. Toward the design of next ion source, database for the voltage holding capability based on experimental results is required and obtained. As a result, the voltage holding capability was found to vary with 67 N power of -0.15 and with 31.7 S power of -0.125 where N is the aperture number and S is the anode surface area. When N = 1100 and S = 2 m$$^{2}$$ are applied to the design of JT-60SA ion source, the factors C are estimated to be 23 and 29, respectively. Therefore, the influence of the local electric field around the apertures is stronger than that of the surface area.

223 (Records 1-20 displayed on this page)