939 resultados para laser ion source


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In 2010 more than 600 radiocarbon samples were measured with the gas ion source at the MIni CArbon DAting System (MICADAS) at ETH Zurich and the number of measurements is rising quickly. While most samples contain less than 50 mu g C at present, the gas ion source is attractive as well for larger samples because the time-consuming graphitization is omitted. Additionally, modern samples are now measured down to 5 per-mill counting statistics in less than 30 min with the recently improved gas ion source. In the versatile gas handling system, a stepping-motor-driven syringe presses a mixture of helium and sample CO2 into the gas ion source, allowing continuous and stable measurements of different kinds of samples. CO2 can be provided in four different ways to the versatile gas interface. As a primary method. CO2 is delivered in glass or quartz ampoules. In this case, the CO2 is released in an automated ampoule cracker with 8 positions for individual samples. Secondly, OX-1 and blank gas in helium can be provided to the syringe by directly connecting gas bottles to the gas interface at the stage of the cracker. Thirdly, solid samples can be combusted in an elemental analyzer or in a thermo-optical OC/EC aerosol analyzer where the produced CO2 is transferred to the syringe via a zeolite trap for gas concentration. As a fourth method, CO2 is released from carbonates with phosphoric acid in septum-sealed vials and loaded onto the same trap used for the elemental analyzer. All four methods allow complete automation of the measurement, even though minor user input is presently still required. Details on the setup, versatility and applications of the gas handling system are given. (C) 2012 Elsevier B.V. All rights reserved.

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The European Rosetta mission on its way to comet 67P/Churyumov-Gerasimenko will remain for more than a year in the close vicinity (1 km) of the comet. The two ROSINA mass spectrometers on board Rosetta are designed to analyze the neutral and ionized volatile components of the cometary coma. However, the relative velocity between the comet and the spacecraft will be minimal and also the velocity of the outgassing particles is below 1km∕s. This combination leads to very low ion energies in the surrounding plasma of the comet, typically below 20eV. Additionally, the spacecraft may charge up to a few volts in this environment. In order to simulate such plasma and to calibrate the mass spectrometers, a source for ions with very low energies had to be developed for the use in the laboratory together with the different gases expected at the comet. In this paper we present the design of this ion source and we discuss the physical parameters of the ion beam like sensitivity, energy distribution, and beam shape. Finally, we show the first ion measurements that have been performed together with one of the two mass spectrometers.

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"The Y-12 Plant of the Clinton Engineer Works was operated by the Tennessee Eastman Corporation under Contract No. W-7401-eng-23 from Januaury 1943 until May 4, 1947, at which time operations were taken over by Carbide and Carbon Chemicals Corporation for the U.S. Atomic Energy Commission under Contract No. W-7405-eng-26"--Page 2 of cover.

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The flow rates of drying and nebulizing gas, heat block and desolvation line temperatures and interface voltage are potential electrospray ionization parameters as they may enhance sensitivity of the mass spectrometer. The conditions that give higher sensitivity of 13 pharmaceuticals were explored. First, Plackett-Burman design was implemented to screen significant factors, and it was concluded that interface voltage and nebulizing gas flow were the only factors that influence the intensity signal for all pharmaceuticals. This fractionated factorial design was projected to set a full 2(2) factorial design with center points. The lack-of-fit test proved to be significant. Then, a central composite face-centered design was conducted. Finally, a stepwise multiple linear regression and subsequently an optimization problem solving were carried out. Two main drug clusters were found concerning the signal intensities of all runs of the augmented factorial design. p-Aminophenol, salicylic acid, and nimesulide constitute one cluster as a result of showing much higher sensitivity than the remaining drugs. The other cluster is more homogeneous with some sub-clusters comprising one pharmaceutical and its respective metabolite. It was observed that instrumental signal increased when both significant factors increased with maximum signal occurring when both codified factors are set at level +1. It was also found that, for most of the pharmaceuticals, interface voltage influences the intensity of the instrument more than the nebulizing gas flowrate. The only exceptions refer to nimesulide where the relative importance of the factors is reversed and still salicylic acid where both factors equally influence the instrumental signal. Graphical Abstract ᅟ.

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To meet the requirements of providing high-intensity heavy ion beams the direct plasma injection scheme (DPIS) was proposed by a RIKEN-CNS-TIT collaboration. In this scheme a radio frequency quadrupole (RFQ) was joined directly with the laser ion source (LIS) without a low-energy beam transport (LEBT) line. To find the best design of the RFQ that will have short length, high transmission efficiency and small emittance growth, beam dynamics designs with equipartitioning design strategy and with matched-only design strategy have been performed, and a comparison of their results has also been done. Impacts of the input beam parameters on transmission efficiency are presented, too. (C) 2008 Elsevier B.V. All rights reserved.

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In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between a laser target and beam extraction position. In direct plasma injection scheme, which uses a laser ion source and a radio frequency quadrupole linac, we can apply relatively higher electric field at beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration such as several tens of milliamperes, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C6+ beam was accelerated. We confirmed that matching condition can be improved by controlling plasma drift distance.

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本文概述了 A > 170 质量区重丰中子同位素研究的主要工作和意义;介绍了 A > 170 重丰中子同位素合成、分离和鉴别方法;详细论述了激光离子源的原理、设计及其同传统离子源相比所具有的优越性;在文章结尾,设计了一个物理实验,实验目的在于:1)寻找 ~(181)Yb新核素;2)揭示天体物理学中~(180m)Ta 的产生问题。我们对反应截面进行了分析,并对产额进行了估计,证明了此实验设计的合理性,进而说明了带激光离子源的同位素分离器适用于产生截面很低的新核素和衰变研究。本文重点讨论了激光离子源的各方面问题:介绍了激光多步共振电离原理和激光离子源原理;具体分析了热毛细管式激光离子源元素选择性的产生及其影响的因素;讨论了在设计、加工过程中的具体问题;描述了所使用的激光技术;通过在线实验验证了热毛细管式激光离子源的元素选择性和分离效率。

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本文介绍了一种新型的用于在线同位素分离器的离子源——激光离子源。这种离子源将会大大提高在线同位素分离器的化学选择性,给新核素的合成及其衰变性质研究注入巨大的活力。论文首先介绍了激光离子源的工作原理和国际上研制激光离子源的情况。其次介绍了我们在研制热管式激光离子源方面取得的以下进展:(1)激光器系统已经可以使用,完成了光路传输与合成系统;(2)研制了一个用于研究激光离子源特性的离线实验装置;(3)获得了铥元素的激光多步共振电离信号,测量了Ta,Nb-Zr合金和内表面涂有了TaC的Nb-Zr合金电离管表面电离电流及激光共振电离电流随温度纷变化曲线,得到了热管式激光离子源的化学选择性,对元素铥的化学选择性可达封50-10000,论文最后对将要做的工作提出了进一步的设想,对激光离子源的前景做了展望。

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Spectrally-peaked proton beams of high charge (Ep ≈ 8 MeV, ΔE ≈ 4 MeV, N ≈ 50 nC ) have been observed from the interaction of an intense laser (>1019Wcm-2) with ultrathinCHfoils, as measured by spectrally-resolved full beam profiles. These beams are reproducibly generated for foil thicknesses 5-100 nm, and exhibit narrowing divergence with decreasing target thickness down to ≈8° for 5 nm. Simulations demonstrate that the narrow energy spread feature is a result of buffered acceleration of protons. The radiation pressure at the front of the target results in asymmetric sheath fields which permeate throughout the target, causing preferential forward acceleration. Due to their higher chargeto-mass ratio, the protons outrun a carbon plasma driven in the relativistic transparency regime.

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Die resonante Laserionisation hat sich als ein universales Verfahren für eine Vielzahl von Anwendungen etabliert, die eine selektive Ionisation bei hoher Effizienz erfordern. Hierzu wurden zwei Lasersysteme mit unterschiedlichen Zielsetzungen und Schwerpunkten entwickelt und in dieser Arbeit angewendet. Im ersten Teil der Arbeit wird die Entwicklung der hochauflösenden Resonanzionisations-Massenspektrometrie zum Ultraspurennachweis von 41Ca vorgestellt. Hierzu wurden drei kontinuierliche Diodenlaser mit einem Quadrupolmassenspektrometer kombiniert. Bei einer Nachweiseffizienz von 1 × 10^−5 konnte eine Nachweisgrenze von 2 × 10^-13 41Ca/totCa erreicht werden. Das in den Routinebetrieb überführte Meßverfahren ermöglichte die Teilnahme an einem interdisziplinären Netzwerk zur Osteoporose-Forschung. In Vergleichsmessungen der Resonanzionisations-Massenspektrometrie mit allen derzeit existierenden Meßverfahren zum 41Ca-Ultraspurennachweis konnte eine sehr gute Übereinstimmung erzielt werden. Der zweite Teil der Arbeit beinhaltet die Adaption eines durchstimmbaren, hochrepetierenden Titan:Saphir-Lasersystem für den Einsatz an Laserionenquellen zur selektiven Erzeugung radioaktiver Ionenstrahlen. Das entwickelte Lasersystem ermöglicht eine effiziente, resonante Anregung des Großteils der Elemente im Periodensystem. Hierzu wurde eine kombinierte Frequenzverdopplungs- und Frequenzverdreifachungseinheit zur Erzeugung höherer Harmonischer aufgebaut. Die Anwendbarkeit eines solchen reinen Festkörper-Lasersystems wurde in zahlreichen off-line Testmessungen sowohl in Mainz als auch an den ISOL Einrichtungen am TRIUMF und ORNL gezeigt und führte zum ersten on-line Einsatz am TRIUMF.