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Search Publications by: Ryan P. Fitzgerald ()

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Displaying 76 - 100 of 135

HOW OLD IS IT? - 241PU/AMNUCLEAR FORENSIC CHRONOLOGY REFERENCE MATERIALS

October 27, 2015
Author(s)
Ryan P. Fitzgerald, Kenneth G. Inn
One material attribute for nuclear forensics is material age. 241Pu is almost always present in uranium- and plutonium-based nuclear weapons, which pose the greatest threat to our security. The in-growth of 241Am due to the decay of 241Pu provides an

Development of an Ultra-Pure, Carrier-Free 209Po Solution Standard

July 23, 2015
Author(s)
Ronald Colle, Ryan P. Fitzgerald, Lizbeth Laureano-Perez
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

Uncertainties in 4-pi-beta-gamma coincidence counting

May 22, 2015
Author(s)
Ryan P. Fitzgerald, Claude Bailat, Christophe Bobin, John Keightley
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 particular, the

Uncertainty evaluation in activity measurements using ionization chambers

May 22, 2015
Author(s)
Marie Noelle Amiot, V Chiste, Ryan P. Fitzgerald, F Juget, Carine Michotte, Andrew Pearce, G Ratel
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 medicine. As a

Uncertainty of nuclear counting

May 22, 2015
Author(s)
Stefaan Pomme, John Keightley, Ryan P. Fitzgerald
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 due to

Two determinations of the 223Ra half-life

May 1, 2015
Author(s)
Denis E. Bergeron, Ryan P. Fitzgerald
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 measurements

Determination of photon emission probabilities for the main gamma-rays of 223Ra in equilibrium with its progeny

March 11, 2015
Author(s)
Leticia S. Pibida, Brian E. Zimmerman, Ryan P. Fitzgerald, Lynne E. King, Jeffrey T. Cessna, Denis E. Bergeron
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 used

A review of NIST primary activity standards for 18F: 1982 to 2013

August 27, 2014
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Bert M. Coursey, Ryan P. Fitzgerald, Brian E. Zimmerman
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 standard

The Half-Life of 209Po : Revisited

August 13, 2014
Author(s)
Ronald Colle, Ryan P. Fitzgerald, Lizbeth Laureano-Perez
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 performed

A New NIST Primary Standardization of 18F

February 1, 2014
Author(s)
Ryan P. Fitzgerald, Brian E. Zimmerman, Denis E. Bergeron, Jeffrey T. Cessna, Leticia S. Pibida, Denise S. Moreira
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 efficiency

Standardization of 237Np

December 4, 2013
Author(s)
Lizbeth Laureano-Perez, Ryan P. Fitzgerald, Ronald Colle
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 using a 3H standard