TY - JOUR T1 - Hold-up and memory effect for carbon in a compact microwave ion source JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1997 A1 - Schneider, R. J. A1 - vonReden, K. F. A1 - Wills, J. S. C. A1 - Diamond, W. T. A1 - Lewis, R. A1 - Savard, G. A1 - Schmeing, H. AB - The production of C+ in a microwave ion source injected with a gaseous CO2 sample has been investigated as an alternative to sample graphitization, A continuous flow of argon gas maintained the discharge, and 20 mu L Of CO2 gas at approximately 1 atm was pulsed into the source through a sample valve closely coupled to the plasma chamber, The C+ component of the beam fell to 1% of its original intensity less than 10 s after the valve was operated. in a separate experiment, the microwave ion source was operated with pure CO2 feed gas and the extracted beam was magnetically analyzed. Efficient breakup of the molecules was observed. These results are considered promising for such applications as accelerator mass spectrometry of C isotopes in gaseous samples. VL - 123 IS - 1-4 N1 - Wt653Times Cited:13Cited References Count:7 JO - Hold-up and memory effect for carbon in a compact microwave ion source ER - TY - JOUR T1 - Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation JF - Radiocarbon Y1 - 1995 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Osborne, E. A. A1 - Hutton, D. L. A1 - vonReden, K. F. A1 - Schneider, R. J. KW - SPECTROMETRY AB - During the four years the Sample Preparation Laboratory (SPL) at the National Ocean Sciences Accelerator Mass Spectrometer (NOSAMS) Facilty has been in operation we have accumulated much data from which we can assess our progress. We evaluate our procedural blanks here and describe modifications in our procedures that have improved our analyses of older samples. In the SPL, we convert three distinct types of samples-seawater, CaCO3 and organic carbon-to CO2 prior to preparing graphite for the accelerator and have distinct procedural blanks for each procedure. Dissolved inorganic carbon (Sigma CO2) is extracted from acidified seawater samples by sparging with a nitrogen carrier gas. We routinely analyze ''line blanks'' by processing CO2 from a C-14-dead source through the entire stripping procedure. Our hydrolysis blank, IAEA C-1, is prepared by acidifying in vacuo with 100% H3PO4 at 60 degrees C overnight, identical to our sample preparation. We use a dead graphite, NBS-21, or a commercially available carbon powder for our organic combustion blank; organic samples are combusted at 850 degrees C for 5 h using CuO to provide the oxidant. Analysis of our water stripping data suggests that one step in the procedure contributes the major portion of the line blank. At present, the contribution from the line blank has no effect on our seawater analyses (fraction modern (fm) between 0.7 and 1.2). Our hydrolysis blanks can have an fm value as low as 0.0006, but are more routinely between 0.0020 and 0.0025. The fm of our best organic combustion blanks is higher than those routinely achieved in other laboratories and we are currently altering our methods to reduce it. VL - 37 SN - 0033-8222 IS - 2 N1 - Ud868Times Cited:16 Cited References Count:6 JO - Radiocarbon ER - TY - JOUR T1 - Automated Sample Processing at the National Ocean Sciences Ams Facility JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Cohen, G. J. A1 - Hutton, D. L. A1 - Osborne, E. A. A1 - vonReden, K. F. A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Jones, G. A. AB - The high throughput and high precision requirements for the NOSAMS facility have made it essential to automate many of the stages in sample processing. These automated procedures increase the sample capacity for the lab while reducing errors in sample preparation. Automation has also allowed sample histories to be recorded and saved in Sybase, a relational data base. VL - 92 IS - 1-4 N1 - Nv547Times Cited:9Cited References Count:1 JO - Automated Sample Processing at the National Ocean Sciences Ams Facility ER - TY - JOUR T1 - Comparative-Study of Fe-C Bead and Graphite Target Performance with the National-Ocean-Science-Ams (Nosams) Facility Recombinator Ion-Source JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Klinedinst, D. B. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Schneider, R. J. A1 - Klouda, G. A. A1 - vonReden, K. F. A1 - Verkouteren, R. M. A1 - Jones, G. A. AB - An accelerator mass spectrometry (AMS) experiment was designed to investigate C-14 target performance for two target types over a range of isotopic concentrations and sample sizes, with a special focus on the ability to measure C-14 in environmental samples having only microgram amounts of carbon. The findings were positive, showing that precision, accuracy, and stability were adequate to determine C-14 to 1% or better in samples containing as little as 25 mug carbon. Satisfactory Poisson uncertainty and target stability were demonstrated down to a level of 7 mug carbon, but experimental data showed that accurate measurements at that level require detailed knowledge of blank variability and mass dependence of the modern carbon calibration factor. VL - 92 IS - 1-4 N1 - Nv547Times Cited:23Cited References Count:13 JO - Comparative-Study of Fe-C Bead and Graphite Target Performance with the National-Ocean-Science-Ams (Nosams) Facility Recombinator Ion-Source ER - TY - JOUR T1 - Methods for Data Screening, Flagging and Error Analysis at the National-Ocean-Sciences-Ams-Facility JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Schneider, R. J. A1 - Jones, G. A. A1 - McNichol, A. P. A1 - vonReden, K. F. A1 - Elder, K. L. A1 - Huang, K. A1 - Kessel, E. D. AB - All data collection, from sample submittal through processing into targets and AMS analysis, is integrated within a large relational database (Sybase). Over 50 tables are linked through key fields. Through structured queries, the information is analysed and presented for a wide variety of applications. Benefits include enhanced quality control, more complete reports to users and more accurate transfer of data among the several laboratories on the network. VL - 92 IS - 1-4 N1 - Nv547Times Cited:14Cited References Count:4 JO - Methods for Data Screening, Flagging and Error Analysis at the National-Ocean-Sciences-Ams-Facility ER -