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Physics

Radiation

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Displaying 151 - 175 of 268

New Methods for Measurement of Neutron Detector Efficiency up to 20 MeV

December 1, 2014
Author(s)
Fred B. Bateman, Allan D. Carlson, N. A. Kornilov, S M. Grimes, T N. Massey, C E. Brient, D E. Carter, J E. O'Donnell, R. C. Haight, N Boukharouba
A new approach to neutron detector effciency has been taken. A neutron detector has been calibrated with a Cf-252 source at low energy. The calibration was extended to higher neutron energies by use of symetric reactions such as A + A ! (2A - 1) + n:

Potential Hazard Due to Induced Radioactivity Secondary to Radiotherapy: The Report of AAPM Task Group 136

December 1, 2014
Author(s)
Fred B. Bateman, Bruce R. Thomadsen, Ravinder Nath, Jonathan Farr, Cal Glisson, Mohammad K. Islam, T. LaFrance, M. E. Moore, X. G. Xu, Mark Yudelev
External-beam radiation therapy mostly uses high-energy photons (x-rays) produced by medical accelerators but many facilities now use proton beams and a few use neutrons. High energy photons offer several advantages over lower energy photons in terms of

The Metrology of a Rastered Spot of X Rays used in Security Screening

November 6, 2014
Author(s)
Lawrence T. Hudson, Jack Leigh Glover, Ronaldo Minniti
In recent times, ionizing radiation has been used around the world to screen persons for non- medical purposes, namely to detect bulk explosives or other contraband hidden on the body including materials not registered by metal detectors. In contrast to

Structural and Dynamical Studies of Acid Mediated Conversion in Amorphous-Calcium-Phosphate Based Dental Composites

October 31, 2014
Author(s)
Fan Zhang, Andrew Allen, Lyle E. Levine, Mark D. Vaudin, Drago Skrtic, Joseph M. Antonucci, Kathleen Hoffman, Anthony A. Giuseppetti, Jan Ilavsky
Amorphous calcium phosphate (ACP) based composites are promising restorative dental materials attributable to ACP's capacity to release calcium and phosphate ions through a complex reaction in which ACP is converted to its crystalline, apatitic form

Path degeneracy and EXAFS analysis of disordered materials

October 24, 2014
Author(s)
Bruce D. Ravel
The analysis of EXAFS data measured on a material with a disordered local configuration environment around the absorbing atom can be challenging due to the proliferation of photoelectron scattering paths that must be considered in the analysis. In the case

New National Air-Kerma Standard for Low-Energy Electronic Brachytherapy Sources

October 6, 2014
Author(s)
Stephen M. Seltzer, C M. O'Brien, Michael Mitch
The purpose of this report is to document the NIST air-kerma measurement standard for the electronic brachytherapy sources, i.e., the Axxent sources of Xoft, Inc., which operate at tube potentials of 50 kV and anode currents of 300 μA. The use of such

Bromination of marine particulate organic matter through oxidative mechanisms

September 14, 2014
Author(s)
Bruce D. Ravel, Alessandra C. Leri, Kathleen Thornton, Lawrence M. Mayer
Although bromine is considered conservative in seawater, it exhibits a well established correlation with organic carbon in marine sediments. This carbon-bromine association was recently attributed to covalent bonding, with organobromine in sinking

Absolute pulse energy measurements of soft x-rays at the Linac Coherent Light Source

August 25, 2014
Author(s)
Uwe Arp, Alexander Sorokin, Ulf Jastrow, Pavle Jurani?, Svea Kreis, Mathias Richter, Yiping Feng, Dennis Nordlund, Kai Tiedtke, Philip Heimann, Bob Nagler, Hae Ja Lee, Stephanie Mack, Marco Cammarata, Oleg Krupin, Marc Messerschmidt, Michael Holmes , Michael Rowen, William Schlotter, Stefan Moeller, Joshua Turner
This paper reports novel measurements of x-ray optical radiation on an absolute scale from a recently developed source of radiation generated in the soft x-ray regime of a free electron laser. We give a brief description of the physics behind the

Post-Irradiation Study of the Alanine Dosimeter

July 14, 2014
Author(s)
Marc F. Desrosiers
Post-irradiation stability of high-dose dosimeters has traditionally been an important measurement influence quantity. Though the exceptional stability of the alanine dosimeter response with time has rendered this factor a non-issue for routine work, the

On the limits of spin-exchange optical pumping of 3He

July 2, 2014
Author(s)
Thomas R. Gentile, T G. Walker, E Babcock, Qiang NMN Ye, Wangchun Chen
Using diode bar lasers spectrally narrowed with chirped volume holographic gratings (VHGs), we have obtained an improvement in the 3He polarization achievable by spin-exchange optical pumping (SEOP). As compared to our past results with lasers narrowed

Effects of Dose Fractionation on the Response of Alanine Dosimetry

June 28, 2014
Author(s)
Marc F. Desrosiers, John Logar, Brad Lundahl
Alanine dosimetry is well established as a transfer standard and is becoming more prevalently used as a routine dosimetry system for radiation processing. Many routine measurement applications in radiation processing involve absorbed dose measurements

Neutron Interferometric Measurement of the Scattering Length Difference Between the Triplet and Singlet States of N-3 He.

June 4, 2014
Author(s)
Michael G. Huber, Muhammad D. Arif, Wei-Chen N. Chen, Thomas R. Gentile, Daniel S. Hussey, T C. Black, Dimitry A. Pushin, F. E. Wiefeldt, C.B Shahi, L Yang
We report a new determination of the n-Helium-3 scattering length difference Δ b = (−5.411 ± 0.031 (statistical) ± 0.039 (systematic) ) fm between the triplet and singlet states using a neutron interferometer. This revises our previous result Δ b = (−5.610

Noble Gas Excimer Scintillation Following Neutron Capture in Boron Thin Films

April 11, 2014
Author(s)
Alan K. Thompson, Jacob McComb, Charles W. Clark, Michael A. Coplan, Mohamad Al-Sheikhly, Robert E. Vest
Far-ultraviolet (FUV) scintillation signals have been measured in heavy noble gases (argon, krypton, xenon) following boron-neutron capture (10B(n,α)7Li) in 10B thin films. The observed scintillation yields are comparable to the yields from some liquid and

Improvements and Extensions of the Neutron Cross Section and Fluence Standards

April 4, 2014
Author(s)
Allan D. Carlson, V G. Pronyaev, R. Capote, F. J. Hambsch, F. Kappeler, C. Lederer, A Mengoni, R O. Nelson, A.J.M Plompen, P Schillebeeckx, S Simakov, S. Tagesen, H Vonach, A Vorobyev, A Wallner
Updated evaluations of the standards are needed within a few years for new versions of several cross section libraries, e.g.; ENDF/B and JEFF, that have been planned. To update the standards, a collaboration, supported by an IAEA Data Development Project

Polarized 3HE Spin Filters for Neutron Science

February 12, 2014
Author(s)
Thomas R. Gentile, Wei-Chen N. Chen
The large spin dependence of the absorption cross section for neutrons by 3He gas provides a method to polarize neutron beams. For certain applications, such polarized 3He-based neutron "spin filters" have advantages over conventional neutron optical

A New NIST Primary Standardization of 18F

February 1, 2014
Author(s)
Ryan P. Fitzgerald, Brian E. Zimmerman, Denis E. Bergeron, Jeffrey T. Cessna, Leticia S. Pibida, Denise S. Moreira
A new primary standardization of 18F by NIST is reported. The standard is based on live-timed beta- gamma anticoincidence counting with confirmatory measurements by three other methods: (i) liquid scintillation (LS) counting using CIEMAT/NIST 3H efficiency
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