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Search Publications by: Ryan P. Fitzgerald (Fed)

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Displaying 1 - 25 of 71

Activity standard and calibrations for 227Th with ingrowing progeny

April 20, 2024
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Brittany Broder, Leticia Pibida, Ryan P. Fitzgerald, Morgan DiGiorgio, Elisa Napoli, Brian E. Zimmerman
Thorium-227 was separated from its progeny and standardized for activity by the triple-to-double coincidence ratio (TDCR) method of liquid scintillation counting. Confirmatory liquid scintillation-based measurements were made using efficiency tracing with

Ambient humidity, the overlooked influencer of radioactivity measurements

November 27, 2023
Author(s)
Stefaan Pomme, Michael P. Unterweger, Ryan P. Fitzgerald, Denis E. Bergeron, Leticia Pibida, International Collaboration
When verifying the validity of the exponential-decay law through 128 precise decay rate measurement series at various nuclear laboratories, minor violations have been observed in the shape of annual cycles in the residuals with different amplitudes and

Liquid scintillation efficiencies, gamma-ray emission intensities, and half-life for Gd-153

November 9, 2023
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Ryan P. Fitzgerald, Gulakhshan Hamad, Lizbeth Laureano-Perez, Leticia Pibida, Brian E. Zimmerman
Gadolinium-153 was standardized for activity by live-timed anticoincidence counting and an ampoule was submitted to the international reference system (SIR). Absolute emission intensities for the main γ rays were determined with calibrated high-purity

Gravimetric deposition of microliter drops with radiometric confirmation

September 9, 2023
Author(s)
Denis E. Bergeron, Richard Essex, Svetlana Nour, Gordon A. Shaw, R. Michael Verkouteren, Ryan P. Fitzgerald
A manual gravimetric dispensing technique is demonstrated using a micropipettor modified for use with removeable microcapillaries. Liquid scintillation sources were prepared from a well-characterized 241Am reference solution, providing a radiometric check

Update of the BIPM comparison BIPM.RI(II)-K1.Co-60 of activity measurements of the radionuclide 60Co to include the 2020 result of the PTB (Germany), the 2020 result of the NIST (United States), the 2020 result of the SMU (Slovakia), the 2021 result of th

March 20, 2023
Author(s)
R Coulon, C Michotte, S Courte, M Nonis, F van Wyngaardt, M Smith, A Bowan, C Keevers, E Clark, M Zarifi, A Ravindra, DB Kulkarni, R Sharma, Marco Capogni, P De Felice, M Capone, P Carconi, A Fazio, C Bobin, R Lins da Silva, A Leiras, J de Almeida Rangel, M Aguiar Leobino da Silva, A Iwahara, Denis E. Bergeron, Jeffrey T. Cessna, Ryan P. Fitzgerald, Lizbeth Laureano-Perez, Leticia Pibida, MW Van Rooy, Jf Lubbe, MJ van Staden, John Keightley, A Pearce, N Ramirez, E Bendall, S Collins, T Ziemek, E Lech, P Saganowski, M Czudek, A Listkowska, O Nahle, Karsten Kossert, M Takacs, M Krivosik, I Bonkova
Since 1976, 30 laboratories have submitted 85 samples of 60Co to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures (BIPM), with comparison identi_er BIPM.RI(II)-K1.Co-60. Recently, the PTB

Isotope Dilution Mass Spectrometry as an Independent Assessment for Mass Measurements of Milligram Quantities of Aqueous Solution

January 1, 2023
Author(s)
Richard Essex, Jacqueline L. Mann, Denis E. Bergeron, Ryan P. Fitzgerald, Svetlana Nour, Gordon A. Shaw, R. Michael Verkouteren
Isotope dilution mass spectrometry was used to independently assess the accuracy of mass measurement methods developed to quantitatively dispense milligram quantities of aqueous solution. Solutions of isotopically enriched 158Gd and enriched 155Gd were

Primary standardization of 212Pb activity by liquid scintillation counting

September 22, 2022
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Ryan P. Fitzgerald, Lizbeth Laureano-Perez, Leticia Pibida, Brian E. Zimmerman
An activity standard for 212Pb in equilibrium with its progeny was realized, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) counting. A Monte Carlo-based approach to estimating uncertainties due to nuclear decay data

Toward a New Primary Standardization of Radionuclide Massic Activity Using Microcalorimetry and Quantitative Milligram-Scale Samples

February 24, 2022
Author(s)
Ryan P. Fitzgerald, Bradley Alpert, Dan Becker, Denis E. Bergeron, Richard Essex, Kelsey Morgan, Svetlana Nour, Galen O'Neil, Dan Schmidt, Gordon A. Shaw, Daniel Swetz, R. Michael Verkouteren, Daikang Yan
We present a new paradigm for the primary standardization of radionuclide activity per mass of solution (Bq/g). Two key enabling capabilities are 4π decay-energy spectrometry using chip-scale sub-Kelvin microcalorimeters and direct realization of mass by

BIPM comparison BIPM.RI(II)-K1.Gd-153 of activity measurements of the radionuclide 153Gd to include the 2020 result of the NIST (United States)

November 25, 2021
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Ryan P. Fitzgerald, Lizbeth Laureano-Perez, Leticia Pibida, Carine Michotte, S Courte, M Nonis, R Coulon, S Judge
Since 1988, 3 laboratories have submitted 5 samples of 153Gd to the International Reference System (SIR) for activity comparison at the Bureau International des Poids et Mesures (BIPM), with comparison identifier BIPM.RI(II)- K1.Gd-153. Recently, the NIST

MICROMETROLOGY IN PURSUIT OF QUANTUM RADIATION STANDARDS

November 9, 2021
Author(s)
Ryan P. Fitzgerald, Zeeshan Ahmed, Denis E. Bergeron, Nikolai Klimov, Dan Schmidt, Ronald Tosh
With the recent redefinition of the SI base units in terms of constants of nature, the race is on to maximize achievable precision by developing primary standards based on quantum metrology, thereby to realize the Quantum SI. For the becquerel (Bq) and

Ra-224 activity, half-life, and 241 keV gamma ray absolute emission intensity: a NIST-NPL bilateral comparison

December 31, 2020
Author(s)
Denis E. Bergeron, Sean Collins, Leticia Pibida, Jeffrey T. Cessna, Ryan P. Fitzgerald, Brian E. Zimmerman, Peter Ivanov, John Keightley, Elisa Napoli
The national metrology institutes for the United Kingdom and the United States have compared activity standards for 224Ra, an -particle emitter of interest as the basis for therapeutic radiopharmaceuticals. Solutions of 224RaCl2 were assayed by absolute

The Next Generation of Current Measurement for Ionization Chambers

September 1, 2020
Author(s)
Ryan P. Fitzgerald, Denis E. Bergeron, Dean G. Jarrett, Neil M. Zimmerman, Carine Michotte, Hansjoerg Scherer, Stephen Giblin, Steven Judge
Re-entrant ionization chambers (ICs) are essential to radionuclide metrology and nuclear medicine for maintaining standards and measuring half-lives. Metrology-quality systems must be precise and stable to 0.1% over many years, and linear from 10^(-14) A

Ohms Law Low-current Calibration System for Ionization Chambers

August 24, 2020
Author(s)
Dean G. Jarrett, Shamith U. Payagala, Ryan P. Fitzgerald, Denis E. Bergeron, Jeffrey T. Cessna, Charles J. Waduwarage Perera, Neil M. Zimmerman
A system for the calibration of electrometers that measure currents from ionization chambers is described. The calibration system uses a 1 GΩ standard resistor in series with a stable voltage source to generate calibration currents from 1 pA to 20 nA

Accurate Integral Counting Using Multi-channel Analyzers

May 1, 2020
Author(s)
Ryan P. Fitzgerald, Lynne E. King
Many techniques in radionuclide metrology rely on accurate measurement of the total count rate, that is integral counting, from a detector. In modern experiments, this can be achieved by integrating the total number of counts in an energy spectrum produced

228Th breakthrough in 224Ra samples: what can we know and when can we know it?

April 6, 2020
Author(s)
Denis E. Bergeron, Ryan P. Fitzgerald, Leticia S. Pibida
Recent renewed interest in radium-224 (224Ra) as a radiotherapeutic agent prompted the development of a primary standard for activity at the National Institute of Standards and Technology (NIST). The 224Ra decay chain includes the emission four alpha

Primary standardization of Ra-224 activity by liquid scintillation counting

October 11, 2019
Author(s)
Denis E. Bergeron, Jeffrey T. Cessna, Ryan P. Fitzgerald, Brian E. Zimmerman, Lizbeth Laureano-Perez, Ronald Colle, Leticia S. Pibida, Elisa Napoli
A standard for 224Ra activity has been developed, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) counting. The standard was confirmed by efficiency tracing and 4παβ(LS)-γ(NaI(Tl)) anticoincidence counting, as well as by 4πγ

On-chip Silicon Photonics Radiation Sensors

September 18, 2019
Author(s)
Nikolai N. Klimov, Zeeshan Ahmed, Lonnie T. Cumberland, Ileana M. Pazos, Ronald E. Tosh, Ryan P. Fitzgerald
We have examined the impact of cobalt-60-ray radiation up to 1 megagray (MGy) absorbed dose on silicon photonic devices. We do not find any systematic impact of radiation on passivated devices, indicating the durability of passivated silicon devices