@article {longworth_radiocarbon_2022,
	title = {Radiocarbon measurement of CO2 from carbonate minerals using a hybrid gas ion source with an open split interface},
	journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	volume = {531},
	year = {2022},
	month = {11/2022},
	pages = {49{\textendash}55},
	abstract = {We have developed a method for measuring radiocarbon in carbonate minerals as CO2 gas via a NEC MCSNICS hybrid sputter gas ion source (HGIS). The method uses helium as a carrier gas to displace CO2 from sample vials to an open split, where a glass capillary samples the mixture for delivery directly to the HGIS. This method skips the gas transfer and quantification steps used in a closed inlet HGIS system, simplifying sample measurement. Samples larger than 8 mg carbonate can be measured. Results from measurements of consensus standards (TIRI I, IAEA C2, and an internal modern shell standard), and samples from a marine core (F14C = 0.4{\textendash}1.15) show that the method agrees well with traditional AMS measurement of the same samples as graphite, and that the 1σ uncertainty is about 1\%. We discuss advantages and disadvantages of continuous flow sample introduction, and the effect of reduced precision on calibrated age-depth models produced using gas-source data.},
	keywords = {Carbonate, Hybrid gas ion source, radiocarbon},
	issn = {0168-583X},
	doi = {10.1016/j.nimb.2022.08.013},
	url = {https://www.sciencedirect.com/science/article/pii/S0168583X2200218X},
	author = {Longworth, Brett E. and Burton, Joshua R. and Pendleton, Simon L. and Moser, Sydney D. and Roberts, Mark L. and Kurz, Mark D.}
}
@article { ISI:000480669600041,
	title = {Annual radiocarbon measurements in a century-old European beech tree (Fagus sylvatica) from coastal northeastern North America},
	journal = {NUCLEAR INSTRUMENTS \& METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS},
	volume = {456},
	year = {2019},
	month = {OCT 1},
	pages = {264-270},
	abstract = {Radiocarbon (C-14) concentrations of annual tree rings from an European beech tree (Fagus sylvatica) from Woods Hole, MA, USA were analyzed at National Ocean Sciences Accelerator Mass Spectrometry facility (NOSAMS) to construct a C-14 bomb curve record from northeastern North America. The C-14 concentration rises from a pre bomb (1895-1955) average of Fraction Modern ((FC)-C-14) = 0.9764 to a peak of 1.8639 in 1964. After 1964, (FC)-C-14 gradually decreases to 1.0611 in 2014. The annual tree-ring radiocarbon content agrees with the atmospheric radiocarbon content of the Northern Hemisphere and is very similar to the radiocarbon concentration of a red oak (Quercus rubra) tree located in Bear Mountain State Park in New York, USA. Infra-annual tree-ring pairs did not produce evidence of a seasonal effect on the radiocarbon concentration, but there were few samples and more study is warranted.},
	issn = {0168-583X},
	doi = {10.1016/j.nimb.2019.03.029},
	author = {Gaylord, Mary C. Lardie and Longworth, Brett E. and Murphy, Keelan and Cobb, Caroline and McNichol, Ann P.}
}
@article {2632,
	title = {Improved C- efficiency and ion beam currents by modifying SNICS cathode material},
	journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	volume = {439},
	year = {2019},
	month = {Jan-01-2019},
	pages = {90 - 93},
	abstract = {We investigated the possibility of increasing the C-14 AMS efficiency and maximizing C- beam currents by modifying sample cathode geometry and material. Previously, we reported results which showed an increase in C- beam current and improved ionization efficiency when reducing the cathode sample well diameter from 1 mm to 0.75 mm and using zinc inserts, pressed into the aluminum cathode holder [4]. In this study we expand that effort by using cathodes with inserts made of Fe, Mo, Ni, Ti, Cu, and Zn. We pressed cathodes with 100 mu g of Oxalic Acid I (OX-I) and ran them to exhaustion. C-12 beam currents, C-14 counts, and graphite weight were used to determine ion source efficiency.},
	keywords = {Cathode, Efficiency, Ion source, SNICS},
	issn = {0168583X},
	doi = {10.1016/j.nimb.2018.11.015},
	url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2\&SrcAuth=Alerting\&SrcApp=Alerting\&DestApp=WOS_CPL\&DestLinkType=FullRecord\&UT=WOS:000455693100015},
	author = {Hlavenka, Joshua D. and Abrams, Henry and Roberts, Mark L. and Longworth, Brett E. and Fallon, Stewart}
}
@article {550,
	title = {A high output, large acceptance injector for the NOSAMS Tandetron AMS system},
	journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
	volume = {361},
	year = {2015},
	note = {Cu2hzTimes Cited:0Cited References Count:13},
	month = {Oct 15},
	pages = {211-216},
	abstract = {We have completed a major upgrade of the National Ocean Sciences AMS Facility (NOSAMS) Tandetron AMS system in two stages. First, the simultaneous (recombinator) injector was replaced with a fast-cycling sequential injector and changes to the low-energy acceleration section. Data after the injector commissioning show an improvement in background, with mean machine background (commercial graphite) of Fm 0.0004 (62 ka). Second, we replaced the original ion source with a high-output 40 sample MCSNICS source. This improved beam currents and raw ratio fractionation, and increased sample to detection efficiency fivefold.},
	issn = {0168-583X},
	doi = {10.1016/j.nimb.2015.04.005},
	author = {Longworth, Brett E. and von Reden, Karl F. and Long, Pat and Roberts, Mark L.}
}
@article {93,
	title = {Carbonate as sputter target material for rapid C-14 AMS},
	journal = {Nuclear Instruments \& Methods in Physics Research Section B-Beam Interactions with Materials and Atoms},
	volume = {294},
	year = {2013},
	note = {id: 2244; PT: J; CT: 12th International Conference on Accelerator Mass Spectrometry (AMS); CY: MAR 20-25, 2011; CL: Wellington, NEW ZEALAND; TC: 0; UT: WOS:000313234300064},
	pages = {328-334},
	abstract = {This paper describes a technique for measuring the C-14 content of carbonate samples by producing C- ions directly in the negative ion sputter source of an accelerator mass spectrometer CAMS) system. This direct analysis of carbonate material eliminates the time and expense of graphite preparation. Powdered carbonate is mixed with titanium powder, loaded into a target cartridge, and compressed. Beam currents for optimally-sized carbonate targets (0.09-0.15 mg C) are typically 10-20\% of those produced by optimally-sized graphite targets (0.5-1 mg C). Modern (>0.8 Fm) samples run by this method have standard deviations of 0.009 Fm or less, and near-modern samples run as unknowns agree with values from traditional hydrolysis/graphite to better than 2\%. Targets with as little as 0.06 mg carbonate produce useable ion currents and results, albeit with increased error and larger blank. In its current state, direct sputtering is best applied to problems where a large number of analyses with lower precision are required. These applications could include age surveys of deep-sea corals for determination of historic population dynamics, to identify samples that would benefit from high precision analysis, and for growth rate studies of organisms forming carbonate skeletons. (C) 2012 Elsevier B.V. All rights reserved.},
	issn = {0168-583X},
	doi = {10.1016/j.nimb.2012.05.014},
	author = {Longworth, Brett E. and Robinson, Laura F. and Roberts, Mark L. and Beaupr{\'e}, Steven R. and Burke, Andrea and W. J. Jenkins}
}
