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Journal Articles

High efficiency indirect geometory crystal analyzer TOF spectrometer; DYANA dedicated to biology, planning in JSNS

Shibata, Kaoru; Tamura, Itaru; Soyama, Kazuhiko; Arai, Masatoshi; Middendorf, H. D.*; Niimura, Nobuo

Proceedings of ICANS-XVI, Volume 1, p.351 - 354, 2003/07

In this research report we describe the design of DYANA, a new neutron spectrometer dedicated for biology, biomaterials, and related soft-matter studies, which will be installed in the material and life science experimental facility project at the JAERI Tokai establishment. The DYANA spectrometer is an indirect-geometry crystal-analyzer instrument and its energy and momentum transfer range are from several 10$$mu$$eV to several meV and from 0.1$$AA ^{-1}$$ to several $$AA ^{-1}$$ , respectively. These specifications will become possible to do the study of protein dynamics analysis.

Journal Articles

Development of micro-strip gas chamber with individual readout

Nakamura, Tatsuya; Masaoka, Sei; Yamagishi, Hideshi; Soyama, Kazuhiko; Aizawa, Kazuya

Proceedings of ICANS-XVI, Volume 1, p.441 - 446, 2003/07

Development of a Micro-Strip Gas Chamber(MSGC) in JAERI is presented. The performances we aim at are counting rate $$>$$10$$^{6}$$${it cps/mm}$$$^{2}$$, position resolution $$<$$1${it mm}$, detection efficiency $$>$$60% at thermal neutron and good n/gamma discrimination. Our two-dimensional gas detector consists of a micro strip plate printed on a polyimide substrate and a high pressure gas chamber which has all the signal lines are directly taken out (256ch individual readout) and withstands the pressure of 10bar $$^{3}$$${it He}$. The individual signal readout opens the way to realize high counting rate and high position resolution at the same time. We carried out range measurements of secondary particles to confirm the range measuring power of the MSGC with that read out method. The measured ranges in the gas of 3bar helium mixed with $$10%$$ ethane is 3mm, 9.5mm for triton and proton, respectively. Those values are well agreed with theoretical estimation and we could show the feasibility of the precise measurement of the ranges by the MSGC.

Journal Articles

Creation of new McStas components of moderators of JSNS for developing new pulse spectrometer

Tamura, Itaru; Aizawa, Kazuya; Harada, Masahide; Shibata, Kaoru; Maekawa, Fujio; Soyama, Kazuhiko; Arai, Masatoshi

Proceedings of ICANS-XVI, Volume 1, p.529 - 539, 2003/07

Moderator components of the McStas code have been created for the design of the spectrometers of JSNS. Three cryogenic moderators are adopted in JSNS, One is a coupled H$$_{2}$$ moderator for high intensity experiments and other two are decoupled H$$_{2}$$ with poisoned or unpoisoned for high resolution moderators. Monte Carlo simulations have turned out to be useful for design of neutron scattering instruments with high complexity. The software package McStas is selected for its own flexibility. Since the characteristics of neutron beams generated from moderators make influence on the performance of pulse neutron spectrometers, it is important to perform the simulation with neutron source component written precisely. Both Energy dependence of neutron spectrum and time structure of neutrons were calculated using NMTC/JAERI97 and MCNP4a codes.The simulation parameters, which describe the pulse shape as a function of time, are optimized. The creation of neutron source components viewed to coupled H$$_{2}$$ moderator and viewed to decoupled H$$_{2}$$ moderator of JSNS are reported.

Journal Articles

Present status of MLF building layout and ancillary facilities

Kaminaga, Masanori; Haga, Katsuhiro; Kinoshita, Hidetaka; Torii, Yoshikatsu; Hino, Ryutaro; Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 1, p.125 - 133, 2003/07

no abstracts in English

Journal Articles

1MW pulse spallation neutron source (JSNS) under the high intensity proton accelerator project

Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 1, p.13 - 24, 2003/07

no abstracts in English

Journal Articles

Optimization of poisoned and unpoisoned decoupled moderators in JSNS

Harada, Masahide; Teshigawara, Makoto; Watanabe, Noboru; Kai, Tetsuya; Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 2, p.697 - 706, 2003/07

For two decoupled moderators in JSNS, optimization studies were performed by model calculations using NMTC/JAM and MCNP-4C codes. The model was based on a realistic Target-Moderator-Reflector Assembly. We assumed a para-hydrogen ratio of 100%. The shape of poisoned and unpoisoned moderators is a canteen type with dimensions of 13$$^W$$$$times$$12$$^H$$$$times$$6.2$$^T$$ cm$$^3$$. A decoupling energy of about 1 eV was adopted to meet the user's requests. As a decoupler material we selected silver-indium-cadmium alloy. It was found that for the decoupled moderators, especially the poisoned moderator, pulse broadening due to a finite beam-extraction angle ($$theta$$) was very serious. Therefore, $$theta$$ for the poisoned and the unpoisoned moderators were limited to be 7.5$$^{circ}$$ and 17.5$$^{circ}$$, respectively. Cadmium (Cd) was selected as a poison material due to higher cut-off energy than gadolinium and higher peak intensity with narrower pulse width. The poison plate will be placed at 25 mm from the viewed surface which meets the user's requirements.

Journal Articles

Silver-indium-cadmium decoupler and liner

Harada, Masahide; Saito, Shigeru; Teshigawara, Makoto; Kawai, Masayoshi*; Kikuchi, Kenji; Watanabe, Noboru; Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 2, p.677 - 687, 2003/07

As a decoupler material for intense neutron sources, we proposed a new composite material based on the (n,$$gamma$$) reaction, silver-indium-cadmium alloy (AIC), which had lettle helium gas production rate and higher decoupling energy ($$sim$$1eV). We compared an AIC decoupler with Cd and B$$_4$$C decouplers from various viewpoints and finally selected AIC as decoupler and liner materials. In the current design, we adopted AIC of 2.5mm thick with a composition of Ag-35wt%Cd and 0.5mm thick with Ag-15wt%In. A decoupler and a liner can be bonded to structural material (Al-alloy) by HIP for water cooling through Al-alloy. To find the optimal HIP condition, small pieces of Ag-Cd and Ag-In ($$phi$$20$$times$$2mm) were enclosed in Al-alloy capsules ($$phi$$22mm, 3mm thick bottom plate and 1mm thick cap) of several Al-alloys. The optimal condition was found to be 500$$^{circ}$$C with a holding time of 60 minutes under a fixed pressure of 100MPa. Large pieces (Ag-Cd: 200$$times$$200$$times$$2.5mm, Ag-In: 200$$times$$200$$times$$0.5mm, A5083 and A6061: 210$$times$$210$$times$$21mm) were also tested aiming at more realistic size conditions.

Journal Articles

Thermal-hydraulic design of J-PARC cold moderators

Aso, Tomokazu; Sato, Hiroshi; Kaminaga, Masanori; Hino, Ryutaro; Monde, Masanori*

Proceedings of ICANS-XVI, Volume 2, p.935 - 944, 2003/07

no abstracts in English

Journal Articles

Cold moderator design of JSNS 1 MW pulse source

Kogawa, Hiroyuki; Ishikura, Shuichi*; Hino, Ryutaro; Kato, Takashi; Aso, Tomokazu; Sato, Hiroshi; Harada, Masahide; Kai, Tetsuya; Teshigawara, Makoto; Maekawa, Fujio; et al.

Proceedings of ICANS-XVI, Volume 2, p.635 - 644, 2003/07

no abstracts in English

Journal Articles

3-D shielding calculation method for 1-MW JSNS

Maekawa, Fujio; Tamura, Masaya

Proceedings of ICANS-XVI, Volume 3, p.1051 - 1058, 2003/07

A three-dimensional (3-D) shielding calculation model for MCNPX was produced for shielding design of 1-MW JSNS. The model included simplified target-moderator-reflector assembly, helium-vessel and neutron beam extraction pipes, shutters, shield blocks, gaps and void spaces between these components, and so on, and could treat streaming effects precisely. The particle splitting and kill method with cell importance parameters was adopted as a variance reduction method. The cell importance parameters for such a large target station of about 15 m in diameter and 12 m in hight in which neutron fluxes attenuated more than 12 orders of magnitude could be determined appropriately by automated iteration calculations. This calculation procedure enabled detailed 3-D shielding design calculations for the whole target station in a short time, i.e., within 2 days, and contributed for progress of shielding designs of JSNS.

Journal Articles

A New method for neutron-beam-line shielding calculation

Maekawa, Fujio; Tamura, Masaya; Kawai, Masayoshi*; Furusaka, Michihiro*; Watanabe, Noboru

Proceedings of ICANS-XVI, Volume 3, p.1247 - 1255, 2003/07

A method for neutron-beam-line shielding calculation with a Monte Carlo code was newly developed. In the first step, components inside the biological shield such as a target-moderator-reflector-assembly and a neutron-beam-line were modeled, and a neutron current distribution along a duct of the neutron-beam-line was calculated. In the second step, decreases of neutron current along the beam-line were regarded as source terms for the beam-line shield, and required beam-line shield thickness was calculated. The most remarkable feature of this method was accurate treatment of the neutron source term distribution along the beam-line in the second step calculation. The followings were evaluated for JSNS by applying this method: (1) neutron-beam-line shield thickness with an empirical formula for estimating shield thickness conveniently, (2) beam stop sizes, (3) dose rates at a sample position when a shutter was closed, and (4) activation level of a To-chopper blade. These results gave conditions for determining the layout of 23 neutron-beam-lines in the experimental hall.

Journal Articles

Target station design of 1 MW spallation neutron source at the high intensity proton accelerator facilities J-PARC

Takada, Hiroshi; Maekawa, Fujio; Honmura, Shiro*; Yoshida, Katsuhiko*; Teraoku, Takuji*; Meigo, Shinichiro; Sakai, Akio*; Kasugai, Yoshimi; Kanechika, Shuji*; Otake, Hidenori*; et al.

Proceedings of ICANS-XVI, Volume 3, p.1115 - 1125, 2003/07

no abstracts in English

Journal Articles

Structural integrity of cross-flow type mercury target

Kogawa, Hiroyuki; Ishikura, Shuichi*; Haga, Katsuhiro; Kinoshita, Hidetaka; Kaminaga, Masanori; Hino, Ryutaro

Proceedings of ICANS-XVI, Volume 3, p.1295 - 1304, 2003/07

no abstracts in English

Journal Articles

Neutronic study on coupled hydrogen moderator for J-PARC spallation neutron source

Kai, Tetsuya; Harada, Masahide; Teshigawara, Makoto; Watanabe, Noboru; Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 3, p.657 - 666, 2003/07

Neutronic design studies were carried out on the J-PARC coupled H$$_{2}$$ moderator. The highest time- and energy- integrated intensity below 15 meV, pulse peak intensity at 2 meV and 10 meV, were given by 100% para-H$$_{2}$$ moderators, but the optimal moderator thickness was different for each: more than 220 mm, about 120 mm and 80 mm, respectively. Finally, we concluded 140 mm was the optimal thickness for the 100% para-H$$_{2}$$ coupled moderator. Cold neutron distributions on the moderator viewed surface were found to exhibit an intensity-enhanced region at a picture frame part near premoderator. This rather peculiar distribution suggested that the moderator and the viewed surface must be designed so as to take the brighter region near premoderator in use. The intensity decreases along with beam-extraction angle to the normal direction down to about 70% at 25.4$$^{rm o}$$. Then, we propose a cylindrical shape coupled moderator which brings about a slight intensity decrease for 0$$^{rm o}$$ but a increase in the averaged intensity over the angles of interest.

Journal Articles

Solid spallation target materials development

Kawai, Masayoshi*; Furusaka, Michihiro; Li, J.-F.*; Kawasaki, Akira*; Yamamura, Tsutomu*; Mehmood, M.*; Kurishita, Hiroaki*; Kikuchi, Kenji; Takenaka, Nobuyuki*; Kiyanagi, Yoshiaki*; et al.

Proceedings of ICANS-XVI, Volume 3, p.1087 - 1096, 2003/07

In order to establish the technique fabricating a thin target slab with a real size, thin tantalum-clad tungsten slab with a hole for a thermocouple was fabricated with the high-precision machinery techniques and the HIP'ing method. The ultrasonic diagnostic showed that tantalum and tungsten bond was perfect. The HIP optimum condition was certified by means of the small punch test as already reported. The electrolytic coating technique in a molten salt was developed to make a thinner tantalum cladding on a tungsten target with a complicated shape, in order to reduce radioactivity from tantalum in an irradiated target.

Journal Articles

Design of mercury cirulation system for J-SNS

Kinoshita, Hidetaka; Haga, Katsuhiro; Kogawa, Hiroyuki; Kaminaga, Masanori; Hino, Ryutaro

Proceedings of ICANS-XVI, Volume 3, p.1305 - 1314, 2003/07

The JAERI and the KEK are promoting a plan to construct the spallation neutron source at the Tokai Research Establishment, JAERI, under J-PARC project. A mercury circulation system has been designed so as to supply mercury to the target stably. Conceptual design is almost finished. But, it was necessary to confirm a mercury pump performance, and more, to investigate erosion rate under the mercury flow as well as an amount of mercury remained on the surface after drain. The mercury pump performance was tested under the mercury flow conditions by using an experimental gear pump, which had almost the same structure as a practical mercury pump to be expected, and the erosion rates in a mercury pipeline as were investigated. The discharged flow rates of the gear pump increased linearly with the rotation speed. Erosion rates obtained under the mercury velocity less than 1.6 m/s was found to be so small. For the amount of remaining mercury on the pipeline, radioactivity of this remaining mercury volume was found to be three-order lower than that of the target casing.

Journal Articles

Validation of radioactivity calculation code system DCHAIN-SP

Kai, Tetsuya; Maekawa, Fujio; Kasugai, Yoshimi; Niita, Koji*; Takada, Hiroshi; Meigo, Shinichiro; Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 3, p.1041 - 1049, 2003/07

A radioactivity calculation code system DCHAIN-SP was validated in view of the following points: (1) Activation cross section data library for the energy region below 20 MeV. (2) NMTC/JAM code for calculation of the nuclide yield induced by the high energy particles above 20 MeV. (3) DCHAIN-SP code system which treats overall nuclide yield by the high energy particles. 42 of activation cross sections and 22 tritium production cross sections were revised so that the DCHAIN-SP calculation could improve its accuracy within 30% for typical materials irradiated by 14-MeV neutrons. The NMTC/JAM code was improved to implement the GEM model for better estimation of light fragment production. Accuracy of the nuclide yield for proton induced reactions in 10 MeV - 10 GeV still remains in the level of a factor of 2 to 3. The DCHAIN-SP code system was employed for the analysis of time evolution of the radioactivity produced in the samples on a thick mercury target bombarded with 2.83 and 24 GeV protons. It is found that the code system agrees with the measured data by a factor of 2 to 3.

Journal Articles

Thick target benchmark test for the code used in the design of high intensity proton accelerator project

Meigo, Shinichiro; Harada, Masahide; Takada, Hiroshi

Proceedings of ICANS-XVI, Volume 3, p.1059 - 1067, 2003/07

In the neutronics design for the J-PARC facilities, transport codes of NMTC/JAM, MCNPX and MARS are used. In order to confirm the predict ability for these codes, it is important to compare with the experiment result. For the validation of the source term of neutron, the calculations are compared with the experimental spectrum of neutrons produced from thick target. Although slightly disagreement exists, NMTC/JAM, MCNPX and MARS are in good agreement with the experiment within by a factor of 2.

Journal Articles

Design of beam incident monitor for spallation neutron target of JSNS

Meigo, Shinichiro; Harada, Masahide; Teraoku, Takuji*; Maekawa, Fujio

Proceedings of ICANS-XVI, Volume 3, p.1175 - 1180, 2003/07

It is important to monitor the proton beam for the high intensity pulse spallation target. Especially for the beam halo, which may irradiate the bulk surrounding the target, it is important to be observed to prevent causing heat spot in the shielding bulk. At JSNS, a proton beam monitors are located at front of the target. These monitors are assembled with the proton beam window. Since this scheme increases the radiation on the monitor due to the beam loss at the windows, it may arise heat deposition on the monitor. Therefore, heat deposition is calculated with NMTC/JAM. It is found that the heat deposition for normal operation is less than 0.1 W/cc.

Journal Articles

Design of beam optics in the proton beam transport line from synchrotron to spallation neutron target

Meigo, Shinichiro; Noda, Fumiaki*; Fujimori, Hiroshi*; Ikeda, Yujiro

Proceedings of ICANS-XVI, Volume 3, p.967 - 976, 2003/07

In J-PARC project, spallation target is irradiated by 3 GeV proton beam of 1 MW. Due to hands on maintenance for the proton beam lines, loss of proton beam is limited less than 1 W/m. Since it is difficult to predict the phase space distribution of the proton beam, we decided that the beam line have to be larger acceptance for 324 $$pi$$ mrad, which is determined by the collimator located in the synchrotron. Distortion of proton beam is caused by the by the instability of angle at the extraction of 3-GeV synchrotron, miss alignment of the magnet, and un-uniformity of the magnet field. In this study, the distortion is calculated. In order to fit the conditions, the stability of extraction angles should be kept smaller than 0.2 mrad. As for the magnetic field, it is found that the uniformity should be kept better 5x10$$^{-4}$$ and 2x10$$^{-3}$$ for bending and quadruple magnets, respectively. It is also found the error of alignments should be limited smaller than 1.0 mm and 1.0 mrad.

Journal Articles

Development of drabkin energy filters for J-PARC project

Yamazaki, Dai; Soyama, Kazuhiko; Ebisawa, Toru*; Tamura, Itaru; Tasaki, Seiji*

Proceedings of ICANS-XVI, Volume 1, p.407 - 415, 2003/06

Drabkin energy filters extract neutrons of required wavelength using spatial neutron spin resonance. If they are applied to pulsed neutrons, they could sharpen pulse width and cut tail neutrons without reducing band-width or peak-intensity. Shaping of J-PARC coupled-moderator pulse by a Drabkin energy filter was simulated. In the simulation, discrete field gradient to Bx is introduced and total field B is varied in accordance with the dominant wavelength at each moment at the filter position. The results suggest that about 90 % or more of tail neutrons from coupled moderator are cut and a fliter with fields of 200 periods could reduce pulse width up to that of decoupled moderator. Effects of fluctuations of width of each half period were studied and it was found that fluctuation within $$pm$$1 % are tolerable for a flipper with field of 100 or 200 periods.

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