Developing Ultra Small-Scale Radiocarbon Sample Measurement at the University of Tokyo

We have developed accelerator mass spectrometry (AMS) measurement techniques for ultra small-size samples ranging from 0.01 to 0.10 mg C with a new type of MC-SNICS ion source system. We can generate 4 times higher ion beam current intensity for ultra-small samples by optimization of graphite position in the target holder with the new ionizer geometry. CO2 gas graphitized in the newly developed vacuum line is pressed to a depth of 1.5 mm from the front of the target holder. This is much deeper than the previous position at 0.35 mm depth. We measured 12C4+ beam currents generated by small standards and ion beam currents (15–30 μA) from the targets in optimized position, lasting 20 min for 0.01 mg C and 65 min for 0.10 mg C. We observed that the measured 14C/12C ratios are unaffected by the difference of ion beam currents ranging from 5 to 30 μA, enabling measurement of ultra-small samples with high precision. Examination of the background samples revealed 1.1 μg of modern and 1 μg of dead carbon contaminations during target graphite preparation. We make corrections for the contamination from both the modern and background components. Reduction of the contamination is necessary for conducting more accurate measurement.

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Alloy surface composition resulting from fabrication, as determined by s.i.m.s. (secondary ion mass spectrometry)

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1980.0092 ◽

1980 ◽

Vol 295 (1413) ◽

pp. 134-135

Keyword(s):

Secondary Ion Mass Spectrometry ◽

Surface Composition ◽

Ion Beam ◽

Sample Surface ◽

Beam Current ◽

Ion Source ◽

Beam Current Density ◽

Dynamic Mode ◽

Static Mode ◽

Subsequent Performance

In s.i.m.s. the sample surface is ion bombarded and the emitted secondary ions are mass analysed. When used in the static mode with very low primary ion beam current densities (10 -11 A/mm 2 ), the technique analyses the outermost atomic layers with the following advantages (Benninghoven 1973, I975): the structural—chemical nature of the surface may be deduced from the masses of the ejected ionized clusters of atoms; detection of hydrogen and its compounds is possible; sensitivity is extremely high (10 -6 monolayer) for a number of elements. Composition profiles are obtained by increasing the primary beam current density (dynamic mode) or by combining the technique in the static mode with ion beam machining with a separate, more powerful ion source. The application of static s.i.m.s. in metallurgy has been explored by analysing a variety of alloy surfaces after fabrication procedures in relation to surface quality and subsequent performance. In a copper—silver eutectic alloy braze it was found that the composition of the solid surface depended markedly on its pretreatment. Generally there was a surface enrichment of copper relative to silver in melting processes while sawing and polishing enriched the surface in silver

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Upgrading the ECR ion source within FAMA

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp1801047e ◽

2018 ◽

Vol 33 (1) ◽

pp. 47-52

Author(s):

Andrey Efremov ◽

Sergey Bogomolov ◽

Vladimir Bekhterev ◽

Aleksandar Dobrosavljevic ◽

Nebojsa Neskovic ◽

...

Keyword(s):

Electron Cyclotron Resonance ◽

Ion Beam ◽

Ion Source ◽

Vacuum System ◽

Multiply Charged Ions ◽

Inlet System ◽

Multiply Charged ◽

Microwave System ◽

Beam Currents ◽

Charged Ions

Recent upgrading of the Facility for Modification and Analysis of Materials with Ion Beams - FAMA, in the Laboratory of Physics of the Vinca Institute of Nuclear Sciences, included the modernization of its electron cyclotron resonance ion source. Since the old ion source was being extensively used for more than 15 years for production of multiply charged ions from gases and solid substances, its complete reconstruction was needed. The main goal was to reconstruct its plasma and injection chambers and magnetic structure, and thus intensify the production of multiply charged ions. Also, it was decided to refurbish its major subsystems - the vacuum system, the microwave system, the gas inlet system, the solid substance inlet system, and the control system. All these improvements have resulted in a substantial increase of ion beam currents, especially in the case of high charge states, with the operation of the ion source proven to be stable and reproducible.

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Current stability to improve AMS precision for cosmogenic 10Be applications

10.5194/egusphere-egu21-16090 ◽

2021 ◽

Author(s):

Ana Carracedo Plumed ◽

Derek Fabel ◽

Richard Shanks

Keyword(s):

Metal Matrix ◽

Ion Beam ◽

Beam Current ◽

Ion Sources ◽

Precipitation Process ◽

Case Scenario ◽

Series Of Experiments ◽

Counting Statistics ◽

Beam Currents ◽

Cosmogenic 10Be

With the present AMS 10Be uncertainties (~2% best case scenario) and the increasing need for more precise cosmogenic 10Be data it has become imperative to improve AMS measurements. Precision depends on counting statistics which in turn depend on ion beam current stability and sample longevity. The ion beam currents are dependent on the metal matrix in which BeO is dispersed; the matrix:BeO ratio; homogeneity of the mixture and the packing of the AMS cathode. We aim to understand the effect of cathode homogeneity in generating stable beam currents. We have performed a series of experiments using different metal matrices (Nb, Ag, Fe) in different forms (solid and in solution). The metals have been added to different stages of the sample precipitation process and both BeO and Be(OH)2 have been pressed into AMS cathodes and analysed at SUERC. We will discuss results of these experiments and introduce an innovative use of polyoxometalates (molibdanate and niobate) to create a homogeneous compound that has the potential to generate stable ion beam currents from sputter ion sources.

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14C AMS Measurements of <100 μG Samples with a High-Current System

Radiocarbon ◽

10.1017/s0033822200018117 ◽

1997 ◽

Vol 40 (1) ◽

pp. 247-253 ◽

Cited By ~ 26

Author(s):

Karl F. Von Reden ◽

Ann P. McNichol ◽

Ann Pearson ◽

Robert J. Schneider

Keyword(s):

Current System ◽

Ion Beam ◽

Beam Current ◽

Small Sample ◽

Small Samples ◽

High Current ◽

Beam Optics ◽

Woods Hole Oceanographic Institution ◽

Factors Affecting ◽

The Past

The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 μg C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One of the main factors affecting the AMS results is the dependence of a number of the beam optics parameters on the extracted ion beam current. The extracted currents range from 0.5 to 10 μA of 12C− for the sample sizes given above. We here discuss the setup of the AMS system and methods for reliable small-sample measurements and give the AMS-related limits to sample size and the measurement uncertainties.

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Target Preparation for Continuous Flow Accelerator Mass Spectrometry

Radiocarbon ◽

10.1017/s0033822200017938 ◽

1997 ◽

Vol 40 (1) ◽

pp. 95-102 ◽

Cited By ~ 6

Author(s):

Robert J. Schneider ◽

J. M. Hayes ◽

Karl F. Von Reden ◽

Ann P. McNichol ◽

T. J. Eglinton ◽

...

Keyword(s):

Mass Spectrometry ◽

Continuous Flow ◽

Ion Beam ◽

Ion Source ◽

Coastal Sediments ◽

Small Samples ◽

Online Measurement ◽

Target Preparation ◽

Practical Limit ◽

Processing Steps

For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 μg C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an “online” measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO2 produced from carbonates. We describe tests using such an ion source.

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FABRICATION AND MODELING OF MICROCHANNEL MILLING USING FOCUSED ION BEAM

International Journal of Nanoscience ◽

10.1142/s0219581x03001425 ◽

2003 ◽

Vol 02 (04n05) ◽

pp. 375-379 ◽

Cited By ~ 5

Author(s):

A. A. TSENG ◽

B. LEELADHARAN ◽

B. LI ◽

I. INSUA ◽

C. D. CHEN

Keyword(s):

Numerical Model ◽

Silicon Wafer ◽

Focused Ion Beam ◽

Ion Beam ◽

Beam Current ◽

Ion Source ◽

Experimental Measurements ◽

Model Predictions

The capability of using Focused Ion Beam (FIB) for milling microchannels is experimentally and theoretically investigated. Microchannel structures are fabricated by a NanoFab 150 FIB machine, using an Arsenic (As2+) ion source. A beam current of 5 pA at 90 keV accelerating energy is used. Several microchannel patternings are milled at various dwell times at pixel spacing of 14.5 nm on top of a 60 nm gold-coated silicon wafer. An analytical/numerical model is developed to predict the FIB milling behavior. By comparing with the experimental measurements, the model predictions have been demonstrated to be reliable for guiding and controlling the milling processes.

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Enhancement in ion beam current with layered-glows in a constricted dc plasma ion source

Review of Scientific Instruments ◽

10.1063/1.3271252 ◽

2010 ◽

Vol 81 (2) ◽

pp. 02B309 ◽

Cited By ~ 2

Author(s):

Yeong-Shin Park ◽

Y. S. Hwang

Keyword(s):

Ion Beam ◽

Beam Current ◽

Ion Source ◽

Dc Plasma ◽

Plasma Ion Source

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FIB/SEM Dual Beam Instrumentation: Slicing, Dicing, Imaging, and More

Microscopy and Microanalysis ◽

10.1017/s1431927600030051 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 796-797

Author(s):

Lucille A. Giannuzzi

Keyword(s):

Metal Ion ◽

Focused Ion Beam ◽

Ion Beam ◽

Chemical Vapor ◽

Deposition Process ◽

Time Frame ◽

Ion Source ◽

Beam Diameter ◽

Dual Beam ◽

Beam Currents

In a focused ion beam (FIB) instrument, ions (typically Ga+) obtained from a liquid metal ion source are accelerated down a column at energies up to ∽ 50 keV. The beam of ions is focused by electrostatic and octopole lens systems and the ion dose (and beam diameter) is controlled using real and/or virtual apertures. Beam sizes in FIB instruments on the order of 5-7 nm may be achieved.The versatility of the FIB instrument enables large regions of material (e.g., 500 μm3) to be removed at high beam currents in just a couple of minutes. Lower beam currents (i.e., beam diameters) are usually used to remove smaller amounts of material within the same time frame (e.g., ∽ 5μm3). The introduction of an organometallic gas in close proximity to the target allows for the deposition of metals, SiO2, and other materials, by an ion beam assisted chemical vapor deposition process.

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