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Author: ryan fitzgerald
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1. Technical Note on Unexpected Bias in NIST 4¿¿ Ionization Chamber Measurements
Published: 4/4/2012
Authors: Michael P Unterweger, Ryan P Fitzgerald
Abstract: The NIST 4π pressurized ionization chamber ,AŠ (PIC ,AŠ) 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 th ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=910074

2. The effect of impurities on calculated activity in the triple-to-double coincidence ratio liquid scintillation method
Published: 3/4/2012
Authors: Denis E Bergeron, Ryan P Fitzgerald, Brian Edward Zimmerman, Jeffrey T Cessna
Abstract: In the triple-to-double coincidence ratio (TDCR) method of liquid scintillation counting, unaccounted or improperly accounted impurities can result in lower-than-expected or higher-than-expected recovered activities, depending on the counting efficie ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=909218

3. NIST Ionization Chamber "A" Sample-Height Corrections
Series: Journal of Research (NIST JRES)
Report Number: 117.003
Published: 2/2/2012
Author: Ryan P Fitzgerald
Abstract: For over 30 years scientists in the NIST radioactivity group have been using their ionization chamber ,AŠ to make measurements of radioactivity and radioactive half-lives. We now have evidence that some of those reported measurements were incorre ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=909843

4. Investigation into the Standardization of Tc-99
Published: 7/30/2010
Authors: Lizbeth Laureano-Perez, Ronald Colle, Ryan P Fitzgerald, Brian Edward Zimmerman, Lonnie Talmadge Cumberland
Abstract: 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 Stan ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=902971

5. Resonance Strength in 22Ne(p,gamma)23Na from Depth Profiling in Aluminum
Published: 4/30/2010
Authors: R Longland, C. Iliadis, J. Cesaratto, A E Champagne, S Daigle, J.R. Newton, Ryan P Fitzgerald
Abstract: 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 ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=905839

6. Charged-Particle Thermonuclear Reaction Rate Evaluation for A=12-40 Nuclei: I. Monte Carlo Method and Statistical Distributions
Published: 4/28/2010
Authors: Ryan P Fitzgerald, R Longland, C. Iliadis, E. Champagne, J.R. Newton, C. Ugalde
Abstract: A new method based on Monte Carlo techniques is presented for evaluating thermonuclear reaction rates. We begin by reviewing commonly applied procedures and point out that reaction rates that have been reported up to now in the literature have no rig ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=842419

7. Charged-Particle Thermonuclear Reaction Rates: II. Tables and Graphs of Reaction Rates and Probability Density Functions.
Published: 4/9/2010
Authors: C. Iliadis, R Longland, A E Champagne, A. Coc, Ryan P Fitzgerald
Abstract: Numerical values of charged-particle thermonuclear reaction rates for nuclei in the A=14-40 region are tabulated. The results are obtained using a method, based on Monte Carlo techniques, that has been described in the preceding paper of this series ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=904290

8. Look at Data to Evaluate Uncertainty: A comment on "Uranium Assay Determination...." by Mathew et al.
Published: 2/25/2010
Author: Ryan P Fitzgerald
Abstract: According to the Guide to the Expression of Uncertainty in Measurement (GUM), the evaluation of uncertainty should be based as much as possible on observed data. In a recent paper, Mathew et al. detailed, for a specific titration-based assay of urani ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=904570

9. A New Primary Standardization of Th-229
Published: 1/7/2010
Authors: Ryan P Fitzgerald, Lizbeth Laureano-Perez, Michelle M. Hammond, Leticia S Pibida, Svetlana Nour, Brian Edward Zimmerman
Abstract: 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 sy ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=903482

10. An Automated Ionization Chamber for Secondary Radioactivity Standards
Published: 12/8/2009
Author: Ryan P Fitzgerald
Abstract: 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 significan ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=903476



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