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The Global ETD Search service is a free service for researchers
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Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 21 to 29 of 29 (0.136 seconds)| 21 |
Pb-Pb Isotopic and X-ray Tomographic Constraints on the Origin of ChondrulesCharles, Christopher 02 August 2013 (has links)
207Pb*/206Pb* chronometry was used to obtain the ages of Ca,Al-rich inclusions (CAIs) and chondrules found in ancient meteorites. Assuming a 238U/235U=137.88, Pb/Pb ages of chondrules in NWA801 (a CR2 meteorite) are 4564.6±1.0 Ma, chondrules in Mokoia (a CV3 chondrite) are 4564.2±1.1Ma, and CAIs in Mokoia are 4567.9±5.4 Ma. The Pb/Pb age of NWA801 chondrules is concordant with 26Al/26Mg ages of CR chondrules. However if a 238U/235U < 137.88 is used, the age for NWA801 chondrules becomes younger by ~1Ma and discordant with 26Al/26Mg ages of CR chondrules. This suggests either a discrepancy with the U compositions or the initial Mg isotopic compositions of NWA801 chondrules. The shapes of NWA801 chondrules, and blebs of FeNi metal in the meteorite matrix, were further studied by 3D X-ray micro-computed tomography (CT). Most chondrules (92%) were ‘armoured’ with one discontinuous layer of FeNi metal. Two layers of FeNi metal (one on the exterior and one concentric through the interior separated by silicate) were rare <8%. Chondrules and matrix blebs occur as oblates, prolate, spheres and triaxial spheroids. It is proposed that the shapes were made free-floating in the nebula likely by flash-melting precursors into molten droplets that were vibrating as harmonic oscillators that ‘froze-in’ their shapes during cooling. Parent-body metamorphism and shock are not likely processes affecting the matrix-bleb and chondrule shapes. Chondrules with ≥2 FeNi metal layers were likely formed by mergers and not by successive deposition and annealing of metal in multiple flash-melting events. Attempts to obtain 207Pb*/206Pb* ages from chondrules and CAIs by thermal extraction (TE)- TIMS were unsuccessful. However LA-ICP-MS was shown to be useful for rapidly determining Pb isotopic trends in meteorites and unknown objects. In particular, it was shown that 137La (T1/2=60ky) should be detectable in recently fallen meteorites using LaF−4 to suppress the 137Ba
isobar during tandem accelerator mass spectrometry combined with a novel instrumental technique for isobar separation.
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Development of the new trigger and data acquisition system for the CMS forward muon spectrometer upgradeVerhagen, Erik 05 March 2015 (has links)
La physique des particules élémentaires, aussi appelé physique des hautes énergies, est l'étude de l'infiniment petit, popularisée récemment par la découverte de nouvelles particules fondamentales permettant de consolider notre connaissance de la matière. Pour réaliser des mesures à une échelle aussi réduite, une méthode consiste à augmenter l’énergie des constituants de la matière, à l'aide d'accélérateur de particules, puis de les briser pour révéler leur constitution. Au-delà de l'intérêt en termes de physique expérimentale, réaliser des expériences de ce type est devenu une prouesse technologique grandissante avec les niveaux d’énergie atteints. La complexité de l’expérience CMS, cadre dans laquelle ce travail a été réalisé, donne une bonne mesure des défis technologiques relevés.<p>Afin d'affiner encore notre connaissance des processus mis en jeu lors collision de particules dans CMS, une mise à niveau du détecteur est prévue avant la fin de cette décennie. Certains sous-détecteurs actuellement installés, et notamment le spectromètre à muon dans la zone des bouchons, sont d’ores et déjà identifiés comme offrant des performances trop faibles pour l'augmentation du nombres d’événements prévu après cette mise à jour. Ce travail propose de réaliser une étude de faisabilité sur l'utilisation d'une technologie alternative pour ce sous-détecteur, notamment le Triple-GEM, pour combler ces limitations.<p>Une première partie de ce travail consiste en l'étude de cette nouvelle technologie de détecteur à gaz. Cependant, la mise en œuvre de cette technologie conduit à des modifications dans le système d'acquisition de données de CMS. La situation actuelle puis les implications d'un point de vue technique des modifications sont donc détaillées par la suite. Enfin, après avoir identifié les composants et les solutions permettant la collecte de résultats à l’échelle de l'ensemble du sous-détecteur, un système d'acquisition de données similaire a été réalisé et est décrit dans une dernière partie de ce travail. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
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名古屋大学タンデトロンAMS14Cシステムの現状と利用(2011)Hase, Kazumaro, Kato, Tomomi, Sakata, Ken, Yoshimitsu, Takahiro, Kondo, Hiroki, Jyomori, Yuka, Ikemori, Kazufumi, Nishida, Masami, Ohta, Tomoko, Miyata, Yoshiki, Ikeda, Akiko, Oda, Hirotaka, Minami, Masayo, Nakamura, Toshio, 長谷, 和磨, 坂田, 健, 吉光, 貴裕, 加藤, ともみ, 近藤, 宏樹, 城森, 由佳, 池盛, 文数, 西田, 真砂美, 太田, 友子, 宮田, 佳樹, 池田, 晃子, 小田, 寛貴, 中村, 俊夫, 南, 雅代 03 1900 (has links)
名古屋大学年代測定総合研究センターシンポジウム報告
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名古屋大学タンデトロンAMS ^<14>C システムの現状と利用(2009)Hayashi, Kazuki, Yamazaki, Kana, Jyomori, Yuka, Matsumoto, Kana, Honjyo, Koji, Nishimoto, Hiroshi, Omori, Takayuki, Honda, Inami, Nishida, Masami, Ohta, Tomoko, Miyata, Yoshiki, Ikeda, Akiko, Oda, Hirotaka, Minami, Masayo, Nakamura, Toshio, 山﨑, 香奈, 城森, 由佳, 松本, 佳納, 本庄, 浩司, 林, 和樹, 西本, 寛, 大森, 貴之, 本田, 印南, 西田, 真砂美, 太田, 友子, 宮田, 佳樹, 池田, 晃子, 小田, 寛貴, 南, 雅代, 中村, 俊夫 03 1900 (has links)
第22回名古屋大学年代測定総合研究センターシンポジウム平成21(2009)年度報告
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プラント・オパール中の炭素抽出とその14C 年代測定の試みMatsuda, Ryuji, Sugiyama, Shinji, Toyama, Shuichi, Tazaki, Hiroyuki, Udatsu, Tetsuro, Nakamura, Toshio, 松田, 隆二, 杉山, 真二, 外山, 秀一, 田崎, 博之, 宇田津, 徹朗, 中村, 俊夫 03 1900 (has links)
名古屋大学年代測定総合研究センターシンポジウム報告
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名古屋大学タンデトロンAMS14Cシステムの現状と利用(2012)Tomiyama, Shinji, Hase, Kazuma, Soda, Aoi, Kato, Tomomi, Jyomori, Yuka, Ikemori, Kazufumi, Nishida, Masami, Ohta, Tomoko, Miyata, Yoshiki, Hakozaki, Masataka, Itoh, Kazumi, Hitoki, Eri, Ikeda, Akiko, Oda, Hirotaka, Minami, Masayo, Nakamura, Toshio, 冨山, 慎二, 長谷, 和磨, 早田, 葵, 加藤, ともみ, 城森, 由佳, 池盛, 文数, 西田, 真砂美, 太田, 友子, 箱崎, 真隆, 宮田, 佳樹, 伊藤, 一充, 一木, 絵理, 池田, 晃子, 小田, 寛貴, 南, 雅代, 中村, 俊夫 03 1900 (has links)
名古屋大学年代測定総合研究センターシンポジウム報告
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^<14>C実験室間の比較研究 : 名古屋大学と原子力機構むつAMSシステムOhta, Tomoko, Kabuto, Shoji, Tanaka, Takayuki, Nakamura, Toshio, 太田, 友子, 甲, 昭二, 田中, 孝幸, 中村, 俊夫 03 1900 (has links)
No description available.
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A Radio Frequency Quadrupole Instrument for use with Accelerator Mass Spectrometry: Application to Low Kinetic Energy Reactive Isobar Suppression and Gas–phase Anion Reaction StudiesEliades, John Alexander 21 August 2012 (has links)
A radio frequency (rf) quadrupole instrument, currently known as an Isobar Separator for Anions (ISA), has been integrated into an Accelerator Mass Spectrometry (AMS) system to facilitate anion–gas reactions before the tandem accelerator. An AMS Cs+ sputter source provided > 15 keV ions that were decelerated in the prototype ISA to < 20 eV for reaction in a single collision cell and re-accelerated for AMS analysis. Reaction based isobar suppression capabilities were assessed for smaller AMS systems and a new technique for gas–phase reaction studies was developed.
Isobar suppression of 36S– and 12C3– for 36Cl analysis, and YF3– and ZrF3– for 90Sr analysis were studied in NO2 with deceleration to < 12 eV. Observed attenuation cross sections, σ [x 10^–15 cm^2], were σ(S– + NO2) = 6.6, σ(C3– + NO2) = 4.2, σ(YF3– + NO2) = 7.6, σ(ZrF3– + NO2) = 19. With 8 mTorr NO2, relative attenuations of S–/Cl– ~ 10^–6, C3–/Cl– ~ 10^–7, YF3–/SrF3– ~ 5 x 10^–5 and ZrF3–/SrF3– ~ 4 x 10^–6 were observed with Cl– ~ 30% and SrF3– > 90% transmission. Current isobar attenuation limits with < 1.75 MV accelerator terminal voltage and ppm impurity levels were calculated to be 36S–/Cl– ~ 4 x 10^–16, 12C3–/Cl– ~ 1.2 x 10^–16, 90YF3–/SrF3– ~ 10^–15 and 90ZrF3–/SrF3– ~ 10^–16.
Using 1.75 MV, four 36Cl reference standards in the range 4 x 10^–13 < 36Cl/Cl < 4 x 10^–11 were analyzed with 8 mTorr NO2. The measured 36Cl/Cl ratios plotted very well against the accepted values. A sample impurity content S/Cl < 6 x 10^–5 was measured and a background level of 36S–/Cl < 9 x 10^–15 was determined.
Useful currents of a wide variety of anions are produced in AMS sputter sources and molecules can be identified relatively unambiguously by stripping fragments from tandem accelerators. Reactions involving YF3–, ZrF3–, S– and SO– + NO2 in the ISA analyzed by AMS are described, and some interesting reactants are identified.
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A Radio Frequency Quadrupole Instrument for use with Accelerator Mass Spectrometry: Application to Low Kinetic Energy Reactive Isobar Suppression and Gas–phase Anion Reaction StudiesEliades, John Alexander 21 August 2012 (has links)
A radio frequency (rf) quadrupole instrument, currently known as an Isobar Separator for Anions (ISA), has been integrated into an Accelerator Mass Spectrometry (AMS) system to facilitate anion–gas reactions before the tandem accelerator. An AMS Cs+ sputter source provided > 15 keV ions that were decelerated in the prototype ISA to < 20 eV for reaction in a single collision cell and re-accelerated for AMS analysis. Reaction based isobar suppression capabilities were assessed for smaller AMS systems and a new technique for gas–phase reaction studies was developed.
Isobar suppression of 36S– and 12C3– for 36Cl analysis, and YF3– and ZrF3– for 90Sr analysis were studied in NO2 with deceleration to < 12 eV. Observed attenuation cross sections, σ [x 10^–15 cm^2], were σ(S– + NO2) = 6.6, σ(C3– + NO2) = 4.2, σ(YF3– + NO2) = 7.6, σ(ZrF3– + NO2) = 19. With 8 mTorr NO2, relative attenuations of S–/Cl– ~ 10^–6, C3–/Cl– ~ 10^–7, YF3–/SrF3– ~ 5 x 10^–5 and ZrF3–/SrF3– ~ 4 x 10^–6 were observed with Cl– ~ 30% and SrF3– > 90% transmission. Current isobar attenuation limits with < 1.75 MV accelerator terminal voltage and ppm impurity levels were calculated to be 36S–/Cl– ~ 4 x 10^–16, 12C3–/Cl– ~ 1.2 x 10^–16, 90YF3–/SrF3– ~ 10^–15 and 90ZrF3–/SrF3– ~ 10^–16.
Using 1.75 MV, four 36Cl reference standards in the range 4 x 10^–13 < 36Cl/Cl < 4 x 10^–11 were analyzed with 8 mTorr NO2. The measured 36Cl/Cl ratios plotted very well against the accepted values. A sample impurity content S/Cl < 6 x 10^–5 was measured and a background level of 36S–/Cl < 9 x 10^–15 was determined.
Useful currents of a wide variety of anions are produced in AMS sputter sources and molecules can be identified relatively unambiguously by stripping fragments from tandem accelerators. Reactions involving YF3–, ZrF3–, S– and SO– + NO2 in the ISA analyzed by AMS are described, and some interesting reactants are identified.
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