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Ryan P. Fitzgerald (Fed)

Ryan Fitzgerald is a physicist in the NIST Radiation Physics division with a focus on development of primary standards for radionuclides for multiple applications (medical, energy, environmental, etc.). He is part of multiple collaborations exploring new and improved methods for measuring radiation and radioactive decay.

NRC Postdoc Opportunities

Projects & Collaborations

Selected Publications

Evidence against solar influence on nuclear decay constants

Denis E. Bergeron, Ryan P. Fitzgerald, Leticia S. Pibida, Stefaan Pomme
The exponential decay of radionuclides as a function of time is a cornerstone of nuclear physics and radionuclide metrology. Decay constants for spontaneous

Uncertainties in 4-pi-beta-gamma coincidence counting

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


Activity standard and calibrations for 227Th with ingrowing progeny

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

Ambient humidity, the overlooked influencer of radioactivity measurements

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

Gravimetric deposition of microliter drops with radiometric confirmation

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

Patents (2018-Present)

Photonic Calorimeter and Process for Performing Calorimetry

NIST Inventors
Ronald Tosh , Zeeshan Ahmed , Ryan P. Fitzgerald and Nikolai Klimov
A photonic calorimeter converts ionizing radiation dose to heat and includes: a radiation absorber, a temperature compensator disposed within the radiation absorber, a compensation waveguide, a compensation resonator, a compensation resonator, a thermal isolator on which the radiation absorber is
A list of radiation-induced materials modifications that are NIST traceable

Photonic Dosimeter and Process for Performing Dosimetry

NIST Inventors
Ronald Tosh , Zeeshan Ahmed , Ryan P. Fitzgerald and Nikolai Klimov
A photonic dosimeter accrues cumulative dose and includes: a substrate; a waveguide disposed on the substrate and that: receives a primary input light; transmits secondary input light from the primary input light to a dosimatrix; receives a secondary output light from the dosimatrix; and produces
Created May 21, 2019, Updated December 8, 2022