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Search Publications by: Michael P. Unterweger (Assoc)

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Displaying 1 - 25 of 54

Uncertainties in Internal Gas Counting

May 22, 2015
Author(s)
Michael P. Unterweger, L Johansson, M Rodriques, A Yunoki, Lisa R. Karam
The uncertainties in internal gas counting can, for the most part, be split into two areas: counting and sample gas measurement uncertainties and the counting uncertainties. The former includes measurements of counting and sample gas quantities and

Uncertainties in Surface Emission Rate Measurements

May 22, 2015
Author(s)
Michael P. Unterweger
The uncertainties in surface emission rates determined by gas-flow proportional counters (multiwired) will be broken down into alpha and beta emission rate determinations. Counting statistics, spectrum analysis, and electronic uncertainties will be

Justification of Shielding Requirements for Plutonium Sources

September 12, 2012
Author(s)
Leticia S. Pibida, Michael P. Unterweger
This report provides a justification for shielding plutonium sources when testing radiation detection instruments against standard performance requirements and test methods. The use of copper as a shielding material is proposed to provide comparable test

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 Handbook 150-23, 2010 ed., National Voluntary Laboratory Accreditation Program (NVLAP) Homeland Security Applications: Radiation Detection Instruments

April 13, 2010
Author(s)
Betty A. Sandoval, Leticia S. Pibida, Gordon Gillerman, Michael P. Unterweger
NIST Handbook 150-23, NVLAP Homeland Security Applications: Radiation Detection Instruments, presents the technical requirements and guidance for the accreditation of laboratories that test radiation detection instruments used in homeland security

Half-life Measurements of Sr82

January 30, 2009
Author(s)
Leticia S. Pibida, Ryan P. Fitzgerald, Michael P. Unterweger, Michelle M. Hammond, Daniel B. Golas
Half-life measurements of 82Sr were performed at the National Institute of Standards and Technology (NIST) using gamma-ray spectrometry and a 4 pressurized ionization chamber. The 82Sr half-life was determined to be 25.36 ± 0.03 days (k=1) using the

Primary Radioactive Gas Standards (Excluding Radon)

October 16, 2008
Author(s)
Michael P. Unterweger
This paper presents an overview of the primary calibration of radioactive gas standards using length-compensated internal gas counters. The principal of length compensation and the effects of high voltage, detector material, and gas pressure are discussed