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1. Development of an Ultra-Pure, Carrier-Free 209Po Solution Standard
Series: Journal of Research (NIST JRES)
Published: 7/23/2015
Authors: Ronald Colle, Ryan P Fitzgerald, Lizbeth Laureano-Perez
Abstract: Ultra-pure, carrier-free 209Po solution standards have been prepared and standardized for their massic alpha-particle emission rate. The standards, which will be disseminated by the National Institute of Standards and Technology (NIST) as Standard Re ...

2. Uncertainties in 4-pi-beta-gamma coincidence counting
Published: 5/22/2015
Authors: Ryan P Fitzgerald, Claude Bailat, Christophe Bobin, John Keightley
Abstract: The 4-pi-beta-gamma coincidence counting method and its close relatives are widely used for the primary standardization of radioactivity. Both the general formalism and specific implementation of these methods have been well-documented. In partic ...

3. Uncertainty evaluation in activity measurements using ionization chambers
Published: 5/22/2015
Authors: Marie Noelle Amiot, V Chiste, Ryan P Fitzgerald, F Juget, Carine Michotte, Andrew Pearce, G Ratel
Abstract: Pressurized re-entrant (or 4π) pressurized ionization chambers (ICs) connected to current- measuring electronics are used for activity measurements of photon emitting radionuclides and some beta emitters in the field of metrology and nuclear ...

4. Uncertainty of nuclear counting
Published: 5/22/2015
Authors: Stefaan Pomme, John Keightley, Ryan P Fitzgerald
Abstract: Nuclear counting is affected by pulse pileup and system dead time which induce rate-related count loss and alter the statistical properties of the counting process. Fundamental equations are presented to predict deviations from Poisson statistics ...

5. Two determinations of the 223Ra half-life
Published: 5/1/2015
Authors: Denis E Bergeron, Ryan P Fitzgerald
Abstract: Ra-223 is an alpha-emitter that is being used as a bone-seeking radiotherapeutic agent. The relatively large uncertainty on its half-life (0.26 %, Bé et al., 2011) is an impediment to precision activity assays. We have performed two series of measure ...

6. Determination of photon emission probabilities for the main gamma-rays of 223Ra in equilibrium with its progeny
Published: 3/11/2015
Authors: Leticia S Pibida, Brian Edward Zimmerman, Ryan P Fitzgerald, Lynne Emily King, Jeffrey T Cessna, Denis E Bergeron
Abstract: The currently published 223Ra gamma-ray emission probabilities display a wide variation in the values depending on the source of the data. The National Institute of Standards and Technology performed activity measurements on a 223Ra solution that was ...

7. A review of NIST primary activity standards for 18F: 1982 to 2013
Series: Journal of Research (NIST JRES)
Published: 8/27/2014
Authors: Denis E Bergeron, Jeffrey T Cessna, Bert M Coursey, Ryan P Fitzgerald, Brian Edward Zimmerman
Abstract: The new NIST activity standardization for 18F differs from results obtained between 1998 and 2008 by 4 %. The new results are considered to be very reliable; they are based on a battery of robust primary measurement techniques and bring the NIST sta ...

8. The Half-Life of 209Po : Revisited
Published: 8/13/2014
Authors: Ronald Colle, Ryan P Fitzgerald, Lizbeth Laureano-Perez
Abstract: A substantial 25 % error in the then known and accepted (102  5) year half-life of 209Po was reported on in 2007. This error was detected from decay data from two separate primary standardizations of a 209Po solution standard, which were perf ...

9. A New NIST Primary Standardization of 18F
Published: 2/1/2014
Authors: Ryan P Fitzgerald, Brian Edward Zimmerman, Denis E Bergeron, Jeffrey T Cessna, Leticia S Pibida, Denise S Moreira
Abstract: A new primary standardization of 18F by NIST is reported. The standard is based on live-timed beta- gamma anticoincidence counting with confirmatory measurements by three other methods: (i) liquid scintillation (LS) counting using CIEMAT/NIST 3H e ...

10. Standardization of 237Np
Published: 12/4/2013
Authors: Lizbeth Laureano-Perez, Ryan P Fitzgerald, Ronald Colle
Abstract: The standardization of 237Np was investigated. The certified massic activity for 237Np was obtained by 4 liquid scintillation (LS) counting with correction for the 233Pa daughter using the CIEMAT/NIST efficiency tracing method ...

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