Papers by James L'Keith Jones
AIP Conference Proceedings, 2003
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AIP Conference Proceedings, 2004
ABSTRACT Standard shock wave measurements provide no information about the structural changes in ... more ABSTRACT Standard shock wave measurements provide no information about the structural changes in the lattice during the generation and propagation of shock waves. It is important to acquire such information to understand the mechanisms of defect formation in laser processing of materials. Positron annihilation spectroscopy has been shown to be a valuable tool to study electron states and open volume defects in solids for more than 40 years. We report the first dynamic measurements of positron annihilation during short‐pulsed laser irradiation of materials. Nanosecond high‐power laser pulses were synchronized with nanosecond bremsstrahlung pulses from a 30 MeV electron linac to irradiate the materials. Bremsstrahlung photons generate positrons inside the material. These positrons, in turn, annihilate with the shocked material’s electrons emitting 511 keV radiation, which is influenced by the momentum distributions of the electrons. Due to positron trapping at defects, structural changes of the lattice are reflected in the Doppler broadening of the 511 keV annihilation peak. Measurements were conducted on crystalline silicon during laser pulses and after laser irradiation. © 2004 American Institute of Physics
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AIP Conference Proceedings, 2003
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AIP Conference Proceedings, 2002
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AIP Conference Proceedings, 2003
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2008 IEEE Nuclear Science Symposium Conference Record, 2008
Single neutron and gamma charge pulses were captured using a fast ADC. These data were used to po... more Single neutron and gamma charge pulses were captured using a fast ADC. These data were used to populate simulated 5-µs active interrogation flash events. Analysis of these simulations revealed that long pulse tail accumulation during the flash leads to an unpredictable charge background for several microseconds after the flash. The existence of this changing background will make retrieving prompt neutron
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AIP Conference Proceedings, 2009
Proof-of-principle measurements are reported demonstrating that multiplicity techniques can be us... more Proof-of-principle measurements are reported demonstrating that multiplicity techniques can be used to identify prompt fission neutrons from photonuclear interrogation under circumstances where the fission neutrons may be accompanied by photodissociated neutrons of an identical energy spectrum, and where the emitted neutrons are naturally bunched in time by the pulsed nature of the interrogating photon beam. The technique shows promise as
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AIP Conference Proceedings, 2003
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AIP Conference Proceedings, 2001
Calculations of the epithermal-neutron yield of photoneutrons from a uranium-beryllium converter ... more Calculations of the epithermal-neutron yield of photoneutrons from a uranium-beryllium converter using a 27 MeV electron linear accelerator have been investigated. In this concept, relativistic electron beams from a 30 MeV LINAC impinge upon a small uranium sphere surrounded by a cylindrical tank of circulating heavy water (D2O) nested in a beryllium cube. The photo-fission neutron spectrum from the uranium
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Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2005
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Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
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Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
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2008 IEEE Nuclear Science Symposium Conference Record, 2008
... Ahmed, William Bertozzi, Alan Hunt, James Johnson, James Jones, Stephen Korbly, Edward Reedy,... more ... Ahmed, William Bertozzi, Alan Hunt, James Johnson, James Jones, Stephen Korbly, Edward Reedy, Heather Seipel, Sean Stave, Scott ... pulsed linear accelerator using bremsstrahlung photons, and with a narrow bandwidth photon source using Compton backscattered photons. ...
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2007 Ieee Nuclear Science Symposium Conference Record, Vols 1-11, 2007
Active interrogation with pulsed bremsstrahlung beams can saturate detectors and produce high cou... more Active interrogation with pulsed bremsstrahlung beams can saturate detectors and produce high count rates of overlapping pulses in the prompt region (<1 mus) after the interrogating pulse. We describe a method to eliminate saturation by modifying the photomultiplier voltage divider and by gating intermediate pairs of dynodes and the anode. To process the high count rate of overlapping pulses, we convert the output current pulses to charge-pulse steps that can be digitally processed more easily and rapidly in real time. We discuss the application to LaBr3, liquid, and plastic scintillators and present some preliminary data.
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Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
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Papers by James L'Keith Jones