U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by: Ryan P. Fitzgerald ()

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 101 - 125 of 135

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

Technical Note on Unexpected Bias in NIST 4p Ionization Chamber Measurements

April 4, 2012
Author(s)
Michael P. Unterweger, Ryan P. Fitzgerald
The NIST 4π pressurized ionization chamber “A” (PIC “A”) has been the mainstay for secondary calibrations of liquid and gaseous gamma-ray emitting sources for the last 40-45 years. It has also been the main instrument used to measure the half-lives of

NIST Ionization Chamber "A" Sample-Height Corrections

February 2, 2012
Author(s)
Ryan P. Fitzgerald
For over 30 years scientists in the NIST radioactivity group have been using their ionization chamber “A” to make measurements of radioactivity and radioactive half-lives. We now have evidence that some of those reported measurements were incorrect due to

Investigation into the Standardization of Tc-99

July 30, 2010
Author(s)
Lizbeth Laureano-Perez, Ronald Colle, Ryan P. Fitzgerald, Brian E. Zimmerman, Lonnie T. Cumberland
The standardization of 99Tc by several primary methods was investigated. This was performed to support a new 99Tc transfer standard that has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as Standard

Monte-Carlo Reaction Rate Evaluation for Astrophysics

June 2, 2010
Author(s)
Ryan P. Fitzgerald, A. Coc, R Longland, A E. Champagne
We present a new evaluation of thermonuclear reaction rates for astrophysics involving proton and a-particle induced reactions, in the target mass range between A=14 and 40, including many radioactive targets. A method based on Monte Carlo techniques is

Resonance Strength in 22Ne(p,gamma)23Na from Depth Profiling in Aluminum

April 30, 2010
Author(s)
R Longland, C. Iliadis, J. Cesaratto, A E. Champagne, S Daigle, J.R. Newton, Ryan P. Fitzgerald
The novel method for extracting absolute resonance strengths has been investigated. By implanting 22Ne ions into a thick aluminum backing, and simultaneously measuring the 22Ne + p and 27Al+p reactions, the strength of the Elab,r = 479 keV resonance in

A New Primary Standardization of Th-229

January 7, 2010
Author(s)
Ryan P. Fitzgerald, Lizbeth Laureano-Perez, Michelle M. Hammond, Leticia S. Pibida, Svetlana Nour, Brian E. Zimmerman
The National Institute of Standards and Technology (NIST) has certified a high-purity Th-229 Standard Reference Material as SRM 4328C, based on live-timed 4-pi alpha,beta-gamma anticoincidence counting (LTAC) of the equilibrium solution. The LTAC system

An Automated Ionization Chamber for Secondary Radioactivity Standards

December 8, 2009
Author(s)
Ryan P. Fitzgerald
We report on the operation and characterization of a new ionization chamber system, called AUTOIC, featuring a commerical digital electrometer and a commerical robotic sample changer. The ralative accuracy of the electrometer was improved significantly