William. E. Kieser | University of Ottawa | Université d'Ottawa (original) (raw)
Papers by William. E. Kieser
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2013
Radioiodine, 129 I is a biophilic and mobile radionuclide, and a major contaminant of concern for... more Radioiodine, 129 I is a biophilic and mobile radionuclide, and a major contaminant of concern for long term radioactive waste disposal. Nuclear fuel reprocessing has released large amounts of anthropogenic 129 I in a number of locations globally; this has led to an increase in the concentration of 129 I and the 129 I/ 127 I ratio in the environment. Therefore, a detailed understanding of its movement and concentration in the environment is essential. While 129 I dispersion has been examined in the vicinity of nuclear activities, little is known about its accumulation in remote regions. Accordingly, we have undertaken reconnaissance sampling in the Arctic as a location that may be affected by 129 I fallout. Samples from large watersheds were collected in northern Canada on a trajectory starting in Whitehorse, Yukon Territory (60°43 0 00 00 N) and moving north to Tsiigehtchic, Northwest Territory (67°26 0 26 00 N). Results show concentrations of 129 I up to 27 Â 10 6 atoms/L are present in Northwest Canada and 129 I/I ratios up to 1.68 Â 10 À10. Annual 129 I fallout ranges from 2.78 Â 10 9 to 7.95 Â 10 9 atoms/m 2 /yr, calculated by normalizing the measured values to watershed area and discharge. These quantities substantially exceed literature values for waters containing only geogenic or cosmogenic production and are similar for all watersheds regardless of watershed area or discharge. Anthropogenic releases of 129 I into the atmosphere or oceans are the major potential sources of 129 I in the Arctic.
The first measurements of the radioactive 135Cs and 134Cs isotopes were made on an accelerator ma... more The first measurements of the radioactive 135Cs and 134Cs isotopes were made on an accelerator mass spectrometer. The natural Ba interference was suppressed using an isobar separator for anions (ISA) in order to measure the less abundant isobaric 134Cs and 135Cs isotopes. It was found that the Ba interference could be suppressed by a factor of 2 × 10^5 while 25% of Cs was transmitted. Furthermore, through comparing the known natural abundance of Ba isotopes to the measured concentration in a sample it was shown that the ISA does not introduce significant mass dependant fractionation at the level of 0.8%. A slow sequential injection analysis technique was developed to measure 135Cs using 134Cs as a reference isotope. This technique also permitted the monitoring of Ba interference. The ionization efficiency of Cs when analyzed in the molecular anion form, CsF2^- , was on the order of 10^−7 while the total measurement efficiency was 1.7×10^−9. The abundance sensitivity of this system w...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
... IAEA-MEL participated in five cruises to the Kara Sea which were organised between 1992 and 1... more ... IAEA-MEL participated in five cruises to the Kara Sea which were organised between 1992 and 1996 by Norwegian, Russian and US institutes to sample seawater, sediment and biota and to perform in situ underwater measurements [4]. Because of the shallow nature of the ...
Rapid Communications in Mass Spectrometry
RATIONALEAn experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument ha... more RATIONALEAn experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument has been used to demonstrate an on‐line separation of HfF5− from its isobar WF5−. This is necessary, in addition to sample preparation chemistry, for measuring 182Hf at natural levels by Accelerator Mass Spectrometry (AMS).METHODS The device utilizes a radiofrequency quadrupole (RFQ) controlled gas cell, wherein anion‐gas reactions at eV energies attenuate the interfering isobars of the analyte molecular anions, leaving HfF5− for AMS analysis. The RFQ also helps to control the multiple scattering resulting from the ion‐gas collisions.RESULTSO2 gas was used in the HfF5−/WF5− separation and WF5− was attenuated by nearly 3 orders of magnitude while maintaining ~75% transmission of HfF5−. It is expected that the transmission and attenuation can be increased by further research.CONCLUSIONS This result advances the possibility of detecting natural 182Hf when AMS is supplemented with an isobar se...
Radiocarbon
The suppression of interferences from atomic and molecular isobars is a key requirement for the e... more The suppression of interferences from atomic and molecular isobars is a key requirement for the extension of accelerator mass spectrometry (AMS) to the analysis of new cosmogenic isotopes and for increasing the range of applications for small AMS systems. In earlier work, it was shown that unwanted isobars can be eliminated by anion-gas reactions (Litherland et al. 2007). Recently, a prototype system in which such reactions could be applied to ions from an AMS ion source, the Isobar Separator for Anions (ISA), was described (Eliades et al. 2009). This system decelerates the beam of rare anions from keV to eV energies, guides them through a single radiofrequency quadrupole (RFQ) gas cell, and re-accelerates them for further analysis in a 2.5MV AMS system. Tests of this system with Cl and S anions and NO2 gas showed a suppression of S with respect to Cl of over 6 orders of magnitude, with a transmission of ~30% for the Cl beam. In this work, results of the analysis of a range of stand...
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
Currently analysis of 36Cl by accelerator mass spectrometry (AMS) requires large facilities for s... more Currently analysis of 36Cl by accelerator mass spectrometry (AMS) requires large facilities for separation of the isobar 36S. Previously, it has been shown possible to suppress S� by >6 orders of magnitude at low energies in a prototype radio-frequency quadrupole (RFQ) instrument by ion reactions in NO2 gas in the injection line of an AMS system. Reaction products for the negative ions S�, SO� and Cl� with NO2, and S� with N2O, have been surveyed in order to understand isobar attenuation plateaus and the losses of analyte ions. Ion energies were at eV levels, but had a large initial energy spread of at least several eV. Under these conditions, the aggregate total S� and SO� cross sections in NO2 were estimated to be 6.6 � 10�15 cm2 and 7.1 � 10�15 cm2 respectively and the major reaction channel observed was electron transfer producing NO2�. Other reaction products observed for S� were SO�, SO2, NS�, and NSO2�. On the other hand, S�, SO� and NS� were found to be largely unreactive...
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
The University of Ottawa, Canada, has installed a multi-element, 3 MV tandem AMS system as the co... more The University of Ottawa, Canada, has installed a multi-element, 3 MV tandem AMS system as the cornerstone of their new Advanced Research Complex and the principal analytical instrument of the André E. Lalonde Accelerator Mass Spectrometry Laboratory. Manufactured by High Voltage Engineering Europa B.V., the Netherlands, it is equipped with a 200 sample ion source, a high resolution, 120° injection magnet, a 90° high energy analysis magnet (mass-energy product 350 MeV-AMU), a 65°, 1.7 m radius electric analyzer and a 2 channel gas ionization detector. It is designed to analyze isotopes ranging from tritium to the actinides and to accommodate the use of fluoride target materials. This system is being extended with a second injection line, consisting of selected components from the IsoTrace Laboratory, University of Toronto. This line will contain a pre-commercial version of the Isobar Separator for Anions, manufactured by Isobarex Corp., Bolton, Ontario, Canada. This instrument uses ...
Nuclear Physics A, 1979
The resonance previously observed at Ex = 6241 keV in the reactions 17O(p, gamma)18F and 14N(alph... more The resonance previously observed at Ex = 6241 keV in the reactions 17O(p, gamma)18F and 14N(alpha, gamma)18F has been found to be a closely separated doublet (DeltaEx = 2.09+/-0.04 keV). Resonance strengths in 17O(p, gamma)18F, 17O(p, alpha)14N and 14N(alpha, gamma)18 have been measured and partial widths for the resonance states have been obtained. The doublet was further investigated by means
ABSTRACT Extending the range of Accelerator Mass Spectrometry (AMS) to the fission products 90Sr ... more ABSTRACT Extending the range of Accelerator Mass Spectrometry (AMS) to the fission products 90Sr and 135,137Cs would offer numerous advantages for non-proliferation surveillance activities. A new method for suppressing the interfering isobars 90Zr (and 90Y) and 135,137Ba using low kinetic energy (<20 eV) gas-phase reactions in an AMS injection line can help achieving this goal in a cost effective way [1]. The reactions occur in a radiofrequency quadrupole (RFQ) cell filled with a low pressure gas, part of a device known as the Isobar Separator for Anions (ISA). Combined with fluoridematrix assisted ionization, this method greatly improves the analytical capabilities of AMS for 90Sr and will enable the direct analysis of 135,137Cs below sub-parts per trillion levels. The ISA alone provides interference suppression factors of 4×10-6 for ZrF3-/SrF3- and 2×10-5 for BaF2-/CsF2-. The general performance improvement provided by the ISA, however, critically depends on the capacity of this device to transmit the wanted anions with a high efficiency and with a stable response to the natural variations of AMS targets. Based on recent SIMION-8.1 studies and on results of a parallel study on the attenuation of other anions, we have developed a pre-commercial design for the ISA. In this design, RFQ rods and split-flow turbo molecular pumps are configured to achieve full control of reaction time, ion energy and fragmentation pathways (chemical and kinetic reactions), and to improve beam transmission through the cell. The mechanical layout will be presented in 3D models using Solid Works; SIMION-8.1 simulations were used to illustrate the importance of optical matching of the RFQ and the front-end DC retardation section of the ISA.
Nuclear Physics A, 1973
... Enrichment as quoted by supplier (YEDA Industries, USA ... Data A7 (1970) 233 41) DA Vermilye... more ... Enrichment as quoted by supplier (YEDA Industries, USA ... Data A7 (1970) 233 41) DA Vermilyea, Acta Metallurgica 1 (1953) 282 42) HE Gove and AE Litherland, Nuclear spectroscopy A, ed. F. AjzenbergSe love (Academic Press, New York, 1960) p. 260 ' F STRUCTURE (I) 273 ...
spie.org
ABSTRACT Damage in CMOS image sensors caused by heavy ions with moderate energy (~10MeV) are disc... more ABSTRACT Damage in CMOS image sensors caused by heavy ions with moderate energy (~10MeV) are discussed through the effects on transistors and photodiodes. SRIM (stopping and range of ions in matter) simulation results of heavy ion radiation damage to CMOS image sensors implemented with standard 0.35µm and 0.18µm technologies are presented. Total ionizing dose, displacement damage and single event damage are described in the context of the simulation. It is shown that heavy ions with an energy in the order of 10 MeV cause significant total ionizing dose and displacement damage around the active region in 0.35µm technology, but reduced effects in 0.18µm technology. The peak of displacement damage moves into the substrate with increasing ion energy. The effect of layer structure in the 0.18 and 0.35 micron technologies on heavy ion damage is also described.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
Some of the continuing research into AMS at IsoTrace: neutral injection AMS, heavy element backgr... more Some of the continuing research into AMS at IsoTrace: neutral injection AMS, heavy element backgrounds, the analysis of non-conducting samples and low level 14C detection is described.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms - NUCL INSTRUM METH PHYS RES B, 2010
A radio-frequency quadrupole ion guided reaction cell, incorporated into a system for generating,... more A radio-frequency quadrupole ion guided reaction cell, incorporated into a system for generating, decelerating and accelerating anions for analysis by accelerator mass spectrometry is described. Tests of this system for the suppression of the unwanted isobar 36S in the analysis of 36Cl and the measurement of a standard 36Cl reference material are reported.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
The operating parameters for a high current caesium sputter source have been modified so that sta... more The operating parameters for a high current caesium sputter source have been modified so that stable beams of anions can be obtained from natural non-conducting samples. This technique has been applied to the analysis of gold and platinum group elements in silicate matrices, particularly olivines. The handling of interferences resulting from the large number of molecular ions produced in such a target, and the effect of differences in the matrices of reference materials are discussed.
Analytica chimica acta, Jan 4, 2014
A simple method was developed to separate Pu and Am using single column extraction chromatography... more A simple method was developed to separate Pu and Am using single column extraction chromatography employing N,N,N',N'-tetra-n-octyldiglycolamide (DGA) resin. Isotope dilution measurements of Am and Pu were performed using accelerator mass spectrometry (AMS) and alpha spectrometry. For maximum adsorption Pu was stabilized in the tetra valent oxidation state in 8M HNO3 with 0.05 M NaNO2 before loading the sample onto the resin. Am(III) was adsorbed also onto the resin from concentrated HNO3, and desorbed with 0.1 M HCl while keeping the Pu adsorbed. The on-column reduction of Pu(IV) to Pu(III) with 0.02 M TiCl3 facilitated the complete desorption of Pu. Interferences (e.g. Ca(2+), Fe(3+)) were washed off from the resin bed with excess HNO3. Using NdF3, micro-precipitates of the separated isotopes were prepared for analysis by both AMS and alpha spectrometry. The recovery was 97.7±5.3% and 95.5±4.6% for (241)Am and (242)Pu respectively in reagents without a matrix. The recoveri...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010
ABSTRACT A method for interfacing an automated combustion unit to a gas ion source for 14C analys... more ABSTRACT A method for interfacing an automated combustion unit to a gas ion source for 14C analysis is described. This method makes use of an actively controlled transfer line which accommodates the relatively fast flow of the output He carrier gas and short time duration during which the CO2 is released from the combustion unit, and provides a constant ratio of CO2 to He carrier gas to the ion source. Details of the active control system are presented and results from the testing of this control are provided.
Rapid Communications in Mass Spectrometry, 2013
An experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument has been us... more An experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument has been used to demonstrate an on-line separation of HfF5(-) from its isobar WF5(-). This is necessary, in addition to sample preparation chemistry, for measuring (182)Hf at natural levels by Accelerator Mass Spectrometry (AMS). The device utilizes a radiofrequency quadrupole (RFQ) controlled gas cell, wherein anion-gas reactions at eV energies attenuate the interfering isobars of the analyte molecular anions, leaving HfF5(-) for AMS analysis. The RFQ also helps to control the multiple scattering resulting from the ion-gas collisions. O2 gas was used in the HfF5(-)/WF5(-) separation and WF5(-) was attenuated by nearly 3 orders of magnitude while maintaining ~75% transmission of HfF5(-). It is expected that the transmission and attenuation can be increased by further research. This result advances the possibility of detecting natural (182)Hf when AMS is supplemented with an isobar separator in the injection system.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2013
ABSTRACT Using targets made with PbF2 matrices, Cs+ sputter sources have been found to yield elem... more ABSTRACT Using targets made with PbF2 matrices, Cs+ sputter sources have been found to yield element-specific patterns of molecular fluoride anions that may be used to enhance the mass spectrometry of certain elements. While the patterns are found similar for all lanthanides and the heavier actinides, substantial differences are found for the lighter actinides. In the case of Pu and U, of all their fluoride anions, PuF4- and UF5- are produced with the highest yield. Mass spectrometry of Pu using PuF4- can provide a partial chemical separation in the ion source, as the yield of UF4- is two orders of magnitude lower than that of the UF5-. This, in turn, reduces scattering of U ions when measuring Pu in the high-energy components of the AMS system. This instrumental reduction of U is advantageous in cases that require rapid Pu analyses as it simplifies the chemistry of Pu/U separation and other steps in the sample processing. In this procedure, Pu can be co-precipitated with another element as a fluoride, which is then mixed with a sufficient amount of PbF2 powder to form a sputter target. A series of tests were carried out and NdF3 was identified as one such suitable carrier. Measurements of Pu+3 at ∼0.85 MV terminal voltage showed that the 239,240,241,242Pu isotopes can be detected with a manageably low background, high efficiency and a 1 fg detection limit. Preliminary tests were carried out using the existing IsoTrace AMS system, modified only by the addition of electronic controls to automatically adjust the terminal voltage and all high-energy electric analyzers, along with the injection magnet bouncer. However, both the injection and detection systems were not designed for this task, so considerable room is available for reducing the detection limit into the ag range with modern AMS systems – such as the one being commissioned at University of Ottawa.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
ABSTRACT
J. Anal. At. Spectrom., 2015
239,240 Pu and 241 Am isotopes can be measured by Accelerator Mass Spectrometry (AMS) using iron ... more 239,240 Pu and 241 Am isotopes can be measured by Accelerator Mass Spectrometry (AMS) using iron oxide and neodymium fluoride matrices. This report summarizes the measurements of 239,240 Pu and 241 Am in oxide and fluoride matrices by isotope dilution using the same accelerator system and sample preparation techniques at A. E. Lalonde AMS Laboratory (AELL), University of Ottawa. The advantages of each method of Pu and Am isotope measurement are assessed by studying the sensitivity, detection limits, and precision of both techniques. Based the ease of sample preparation, efficiency of ionization, and sensitivity, the fluoride method has an edge. The separation of 239,240 Pu and 241 Am from the sample matrix using a single extraction chromatography column prepared with DGA resin, and their measurements by AMS in fluoride matrices, was tested using the low level certified reference material (IAEA-414). The measured concentrations of 239,240 Pu and 241 Am agreed with the concentrations in the standard reference material.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2013
Radioiodine, 129 I is a biophilic and mobile radionuclide, and a major contaminant of concern for... more Radioiodine, 129 I is a biophilic and mobile radionuclide, and a major contaminant of concern for long term radioactive waste disposal. Nuclear fuel reprocessing has released large amounts of anthropogenic 129 I in a number of locations globally; this has led to an increase in the concentration of 129 I and the 129 I/ 127 I ratio in the environment. Therefore, a detailed understanding of its movement and concentration in the environment is essential. While 129 I dispersion has been examined in the vicinity of nuclear activities, little is known about its accumulation in remote regions. Accordingly, we have undertaken reconnaissance sampling in the Arctic as a location that may be affected by 129 I fallout. Samples from large watersheds were collected in northern Canada on a trajectory starting in Whitehorse, Yukon Territory (60°43 0 00 00 N) and moving north to Tsiigehtchic, Northwest Territory (67°26 0 26 00 N). Results show concentrations of 129 I up to 27 Â 10 6 atoms/L are present in Northwest Canada and 129 I/I ratios up to 1.68 Â 10 À10. Annual 129 I fallout ranges from 2.78 Â 10 9 to 7.95 Â 10 9 atoms/m 2 /yr, calculated by normalizing the measured values to watershed area and discharge. These quantities substantially exceed literature values for waters containing only geogenic or cosmogenic production and are similar for all watersheds regardless of watershed area or discharge. Anthropogenic releases of 129 I into the atmosphere or oceans are the major potential sources of 129 I in the Arctic.
The first measurements of the radioactive 135Cs and 134Cs isotopes were made on an accelerator ma... more The first measurements of the radioactive 135Cs and 134Cs isotopes were made on an accelerator mass spectrometer. The natural Ba interference was suppressed using an isobar separator for anions (ISA) in order to measure the less abundant isobaric 134Cs and 135Cs isotopes. It was found that the Ba interference could be suppressed by a factor of 2 × 10^5 while 25% of Cs was transmitted. Furthermore, through comparing the known natural abundance of Ba isotopes to the measured concentration in a sample it was shown that the ISA does not introduce significant mass dependant fractionation at the level of 0.8%. A slow sequential injection analysis technique was developed to measure 135Cs using 134Cs as a reference isotope. This technique also permitted the monitoring of Ba interference. The ionization efficiency of Cs when analyzed in the molecular anion form, CsF2^- , was on the order of 10^−7 while the total measurement efficiency was 1.7×10^−9. The abundance sensitivity of this system w...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
... IAEA-MEL participated in five cruises to the Kara Sea which were organised between 1992 and 1... more ... IAEA-MEL participated in five cruises to the Kara Sea which were organised between 1992 and 1996 by Norwegian, Russian and US institutes to sample seawater, sediment and biota and to perform in situ underwater measurements [4]. Because of the shallow nature of the ...
Rapid Communications in Mass Spectrometry
RATIONALEAn experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument ha... more RATIONALEAn experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument has been used to demonstrate an on‐line separation of HfF5− from its isobar WF5−. This is necessary, in addition to sample preparation chemistry, for measuring 182Hf at natural levels by Accelerator Mass Spectrometry (AMS).METHODS The device utilizes a radiofrequency quadrupole (RFQ) controlled gas cell, wherein anion‐gas reactions at eV energies attenuate the interfering isobars of the analyte molecular anions, leaving HfF5− for AMS analysis. The RFQ also helps to control the multiple scattering resulting from the ion‐gas collisions.RESULTSO2 gas was used in the HfF5−/WF5− separation and WF5− was attenuated by nearly 3 orders of magnitude while maintaining ~75% transmission of HfF5−. It is expected that the transmission and attenuation can be increased by further research.CONCLUSIONS This result advances the possibility of detecting natural 182Hf when AMS is supplemented with an isobar se...
Radiocarbon
The suppression of interferences from atomic and molecular isobars is a key requirement for the e... more The suppression of interferences from atomic and molecular isobars is a key requirement for the extension of accelerator mass spectrometry (AMS) to the analysis of new cosmogenic isotopes and for increasing the range of applications for small AMS systems. In earlier work, it was shown that unwanted isobars can be eliminated by anion-gas reactions (Litherland et al. 2007). Recently, a prototype system in which such reactions could be applied to ions from an AMS ion source, the Isobar Separator for Anions (ISA), was described (Eliades et al. 2009). This system decelerates the beam of rare anions from keV to eV energies, guides them through a single radiofrequency quadrupole (RFQ) gas cell, and re-accelerates them for further analysis in a 2.5MV AMS system. Tests of this system with Cl and S anions and NO2 gas showed a suppression of S with respect to Cl of over 6 orders of magnitude, with a transmission of ~30% for the Cl beam. In this work, results of the analysis of a range of stand...
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
Currently analysis of 36Cl by accelerator mass spectrometry (AMS) requires large facilities for s... more Currently analysis of 36Cl by accelerator mass spectrometry (AMS) requires large facilities for separation of the isobar 36S. Previously, it has been shown possible to suppress S� by >6 orders of magnitude at low energies in a prototype radio-frequency quadrupole (RFQ) instrument by ion reactions in NO2 gas in the injection line of an AMS system. Reaction products for the negative ions S�, SO� and Cl� with NO2, and S� with N2O, have been surveyed in order to understand isobar attenuation plateaus and the losses of analyte ions. Ion energies were at eV levels, but had a large initial energy spread of at least several eV. Under these conditions, the aggregate total S� and SO� cross sections in NO2 were estimated to be 6.6 � 10�15 cm2 and 7.1 � 10�15 cm2 respectively and the major reaction channel observed was electron transfer producing NO2�. Other reaction products observed for S� were SO�, SO2, NS�, and NSO2�. On the other hand, S�, SO� and NS� were found to be largely unreactive...
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
The University of Ottawa, Canada, has installed a multi-element, 3 MV tandem AMS system as the co... more The University of Ottawa, Canada, has installed a multi-element, 3 MV tandem AMS system as the cornerstone of their new Advanced Research Complex and the principal analytical instrument of the André E. Lalonde Accelerator Mass Spectrometry Laboratory. Manufactured by High Voltage Engineering Europa B.V., the Netherlands, it is equipped with a 200 sample ion source, a high resolution, 120° injection magnet, a 90° high energy analysis magnet (mass-energy product 350 MeV-AMU), a 65°, 1.7 m radius electric analyzer and a 2 channel gas ionization detector. It is designed to analyze isotopes ranging from tritium to the actinides and to accommodate the use of fluoride target materials. This system is being extended with a second injection line, consisting of selected components from the IsoTrace Laboratory, University of Toronto. This line will contain a pre-commercial version of the Isobar Separator for Anions, manufactured by Isobarex Corp., Bolton, Ontario, Canada. This instrument uses ...
Nuclear Physics A, 1979
The resonance previously observed at Ex = 6241 keV in the reactions 17O(p, gamma)18F and 14N(alph... more The resonance previously observed at Ex = 6241 keV in the reactions 17O(p, gamma)18F and 14N(alpha, gamma)18F has been found to be a closely separated doublet (DeltaEx = 2.09+/-0.04 keV). Resonance strengths in 17O(p, gamma)18F, 17O(p, alpha)14N and 14N(alpha, gamma)18 have been measured and partial widths for the resonance states have been obtained. The doublet was further investigated by means
ABSTRACT Extending the range of Accelerator Mass Spectrometry (AMS) to the fission products 90Sr ... more ABSTRACT Extending the range of Accelerator Mass Spectrometry (AMS) to the fission products 90Sr and 135,137Cs would offer numerous advantages for non-proliferation surveillance activities. A new method for suppressing the interfering isobars 90Zr (and 90Y) and 135,137Ba using low kinetic energy (<20 eV) gas-phase reactions in an AMS injection line can help achieving this goal in a cost effective way [1]. The reactions occur in a radiofrequency quadrupole (RFQ) cell filled with a low pressure gas, part of a device known as the Isobar Separator for Anions (ISA). Combined with fluoridematrix assisted ionization, this method greatly improves the analytical capabilities of AMS for 90Sr and will enable the direct analysis of 135,137Cs below sub-parts per trillion levels. The ISA alone provides interference suppression factors of 4×10-6 for ZrF3-/SrF3- and 2×10-5 for BaF2-/CsF2-. The general performance improvement provided by the ISA, however, critically depends on the capacity of this device to transmit the wanted anions with a high efficiency and with a stable response to the natural variations of AMS targets. Based on recent SIMION-8.1 studies and on results of a parallel study on the attenuation of other anions, we have developed a pre-commercial design for the ISA. In this design, RFQ rods and split-flow turbo molecular pumps are configured to achieve full control of reaction time, ion energy and fragmentation pathways (chemical and kinetic reactions), and to improve beam transmission through the cell. The mechanical layout will be presented in 3D models using Solid Works; SIMION-8.1 simulations were used to illustrate the importance of optical matching of the RFQ and the front-end DC retardation section of the ISA.
Nuclear Physics A, 1973
... Enrichment as quoted by supplier (YEDA Industries, USA ... Data A7 (1970) 233 41) DA Vermilye... more ... Enrichment as quoted by supplier (YEDA Industries, USA ... Data A7 (1970) 233 41) DA Vermilyea, Acta Metallurgica 1 (1953) 282 42) HE Gove and AE Litherland, Nuclear spectroscopy A, ed. F. AjzenbergSe love (Academic Press, New York, 1960) p. 260 ' F STRUCTURE (I) 273 ...
spie.org
ABSTRACT Damage in CMOS image sensors caused by heavy ions with moderate energy (~10MeV) are disc... more ABSTRACT Damage in CMOS image sensors caused by heavy ions with moderate energy (~10MeV) are discussed through the effects on transistors and photodiodes. SRIM (stopping and range of ions in matter) simulation results of heavy ion radiation damage to CMOS image sensors implemented with standard 0.35µm and 0.18µm technologies are presented. Total ionizing dose, displacement damage and single event damage are described in the context of the simulation. It is shown that heavy ions with an energy in the order of 10 MeV cause significant total ionizing dose and displacement damage around the active region in 0.35µm technology, but reduced effects in 0.18µm technology. The peak of displacement damage moves into the substrate with increasing ion energy. The effect of layer structure in the 0.18 and 0.35 micron technologies on heavy ion damage is also described.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
Some of the continuing research into AMS at IsoTrace: neutral injection AMS, heavy element backgr... more Some of the continuing research into AMS at IsoTrace: neutral injection AMS, heavy element backgrounds, the analysis of non-conducting samples and low level 14C detection is described.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms - NUCL INSTRUM METH PHYS RES B, 2010
A radio-frequency quadrupole ion guided reaction cell, incorporated into a system for generating,... more A radio-frequency quadrupole ion guided reaction cell, incorporated into a system for generating, decelerating and accelerating anions for analysis by accelerator mass spectrometry is described. Tests of this system for the suppression of the unwanted isobar 36S in the analysis of 36Cl and the measurement of a standard 36Cl reference material are reported.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
The operating parameters for a high current caesium sputter source have been modified so that sta... more The operating parameters for a high current caesium sputter source have been modified so that stable beams of anions can be obtained from natural non-conducting samples. This technique has been applied to the analysis of gold and platinum group elements in silicate matrices, particularly olivines. The handling of interferences resulting from the large number of molecular ions produced in such a target, and the effect of differences in the matrices of reference materials are discussed.
Analytica chimica acta, Jan 4, 2014
A simple method was developed to separate Pu and Am using single column extraction chromatography... more A simple method was developed to separate Pu and Am using single column extraction chromatography employing N,N,N',N'-tetra-n-octyldiglycolamide (DGA) resin. Isotope dilution measurements of Am and Pu were performed using accelerator mass spectrometry (AMS) and alpha spectrometry. For maximum adsorption Pu was stabilized in the tetra valent oxidation state in 8M HNO3 with 0.05 M NaNO2 before loading the sample onto the resin. Am(III) was adsorbed also onto the resin from concentrated HNO3, and desorbed with 0.1 M HCl while keeping the Pu adsorbed. The on-column reduction of Pu(IV) to Pu(III) with 0.02 M TiCl3 facilitated the complete desorption of Pu. Interferences (e.g. Ca(2+), Fe(3+)) were washed off from the resin bed with excess HNO3. Using NdF3, micro-precipitates of the separated isotopes were prepared for analysis by both AMS and alpha spectrometry. The recovery was 97.7±5.3% and 95.5±4.6% for (241)Am and (242)Pu respectively in reagents without a matrix. The recoveri...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010
ABSTRACT A method for interfacing an automated combustion unit to a gas ion source for 14C analys... more ABSTRACT A method for interfacing an automated combustion unit to a gas ion source for 14C analysis is described. This method makes use of an actively controlled transfer line which accommodates the relatively fast flow of the output He carrier gas and short time duration during which the CO2 is released from the combustion unit, and provides a constant ratio of CO2 to He carrier gas to the ion source. Details of the active control system are presented and results from the testing of this control are provided.
Rapid Communications in Mass Spectrometry, 2013
An experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument has been us... more An experimental Isobar Separator for Accelerator Mass Spectrometry (ISAMS) instrument has been used to demonstrate an on-line separation of HfF5(-) from its isobar WF5(-). This is necessary, in addition to sample preparation chemistry, for measuring (182)Hf at natural levels by Accelerator Mass Spectrometry (AMS). The device utilizes a radiofrequency quadrupole (RFQ) controlled gas cell, wherein anion-gas reactions at eV energies attenuate the interfering isobars of the analyte molecular anions, leaving HfF5(-) for AMS analysis. The RFQ also helps to control the multiple scattering resulting from the ion-gas collisions. O2 gas was used in the HfF5(-)/WF5(-) separation and WF5(-) was attenuated by nearly 3 orders of magnitude while maintaining ~75% transmission of HfF5(-). It is expected that the transmission and attenuation can be increased by further research. This result advances the possibility of detecting natural (182)Hf when AMS is supplemented with an isobar separator in the injection system.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2013
ABSTRACT Using targets made with PbF2 matrices, Cs+ sputter sources have been found to yield elem... more ABSTRACT Using targets made with PbF2 matrices, Cs+ sputter sources have been found to yield element-specific patterns of molecular fluoride anions that may be used to enhance the mass spectrometry of certain elements. While the patterns are found similar for all lanthanides and the heavier actinides, substantial differences are found for the lighter actinides. In the case of Pu and U, of all their fluoride anions, PuF4- and UF5- are produced with the highest yield. Mass spectrometry of Pu using PuF4- can provide a partial chemical separation in the ion source, as the yield of UF4- is two orders of magnitude lower than that of the UF5-. This, in turn, reduces scattering of U ions when measuring Pu in the high-energy components of the AMS system. This instrumental reduction of U is advantageous in cases that require rapid Pu analyses as it simplifies the chemistry of Pu/U separation and other steps in the sample processing. In this procedure, Pu can be co-precipitated with another element as a fluoride, which is then mixed with a sufficient amount of PbF2 powder to form a sputter target. A series of tests were carried out and NdF3 was identified as one such suitable carrier. Measurements of Pu+3 at ∼0.85 MV terminal voltage showed that the 239,240,241,242Pu isotopes can be detected with a manageably low background, high efficiency and a 1 fg detection limit. Preliminary tests were carried out using the existing IsoTrace AMS system, modified only by the addition of electronic controls to automatically adjust the terminal voltage and all high-energy electric analyzers, along with the injection magnet bouncer. However, both the injection and detection systems were not designed for this task, so considerable room is available for reducing the detection limit into the ag range with modern AMS systems – such as the one being commissioned at University of Ottawa.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
ABSTRACT
J. Anal. At. Spectrom., 2015
239,240 Pu and 241 Am isotopes can be measured by Accelerator Mass Spectrometry (AMS) using iron ... more 239,240 Pu and 241 Am isotopes can be measured by Accelerator Mass Spectrometry (AMS) using iron oxide and neodymium fluoride matrices. This report summarizes the measurements of 239,240 Pu and 241 Am in oxide and fluoride matrices by isotope dilution using the same accelerator system and sample preparation techniques at A. E. Lalonde AMS Laboratory (AELL), University of Ottawa. The advantages of each method of Pu and Am isotope measurement are assessed by studying the sensitivity, detection limits, and precision of both techniques. Based the ease of sample preparation, efficiency of ionization, and sensitivity, the fluoride method has an edge. The separation of 239,240 Pu and 241 Am from the sample matrix using a single extraction chromatography column prepared with DGA resin, and their measurements by AMS in fluoride matrices, was tested using the low level certified reference material (IAEA-414). The measured concentrations of 239,240 Pu and 241 Am agreed with the concentrations in the standard reference material.