Positron Transmission and Scattering Measurements Using Superposition of Annihilation Line Shapes: Backscatter Coefficients

MacKenzie, I. K.; Shulte, C. W.; Jackman, T. E.; Campbell, John L.

doi:10.1103/physreva.7.135

Cited by 59 publications

(10 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As neither the nickel single crystal reference sample nor the unaffected surfaces of Nimonic 80A provided this component when measured by the same positron source, we should not consider this as a source correction. However, on the other hand, the large backscatter coefficient of nickel and chromium against kapton [18,19] and the rough surface might explain some positronium formation on strained surfaces.…”

Section: Positron Annihilationmentioning

confidence: 94%

“…The formation of nanostructured glazed surfaces during the sliding wear processes can be understood, in a general way, in terms of the mechanisms that were described in previous publications [17,18]. The initial events responsible for generating the glaze layer involve intermixing of the debris generated from the contacting surfaces, oxidation, further mixing (the lack of any composition gradient in the glaze layer indicates efficient intermixing of the components constituting the layer), repeated welding and fracture and final consolidation.…”

Section: Observations On Glaze Surface Layermentioning

confidence: 99%

See 1 more Smart Citation

Investigations of microstructures and defect structures in wear affected region created on Nimonic 80A during high temperature wear

Datta

Inman

et al. 2005

Tribol Lett

View full text Add to dashboard Cite

The microstructures of a wear induced surface glazed layers formed during sliding wear of Nimonic 80A against Stellite 6 at 20-750°C using a speed of 0.314 m s )1 under a load of 7 N have been investigated using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in combination with energy dispersive X-ray (EDX) analysis. The defects formed in the glazed layers were measured by positron lifetime spectroscopy. The results indicate the formation of a wear resistant nanostructured glazed layer. Positron lifetime and Doppler-broadening measurements demonstrated that the defects (mainly dislocations) existed in the glazed layers at low temperatures which increasing wear test temperature led to decrease in defects density. Positron measurements also suggested that, at the annealing temperature (1200°C), the presence of dislocations might lead to the formation of ordered or partially ordered regions in Nimonic 80A.

show abstract

Section: Positron Annihilationmentioning

confidence: 94%

Section: Observations On Glaze Surface Layermentioning

confidence: 99%

Investigations of microstructures and defect structures in wear affected region created on Nimonic 80A during high temperature wear

Datta

Inman

et al. 2005

Tribol Lett

View full text Add to dashboard Cite

show abstract

“…MacKenzie et al 18 measured positron backscatter coefficients R for a wide range of elements using a geometry similar to PALS, the most satisfactory fit over the entire Z range was found to be R = 0.342log 10 Z − 0.146. Several empirical backscatter coefficient expressions have been reported.…”

Section: Introductionmentioning

confidence: 99%

Positron lifetimes of polycrystalline metals: A positron source correction study

McGuire

Keeble

2006

Journal of Applied Physics

View full text Add to dashboard Cite

Saturated electric field effect at semi-insulating GaAs-metal junctions studied with a low energy positron beam Positron lifetime measurements have been made on a series of polycrystalline metals with atomic numbers varying from 13 to 82, using positron sources deposited on Ni, Al, and Kapton support foils. Bulk positron lifetimes for Al, Ni, Zr, In, and Pb are reported. The results support previous assignments of monovacancy lifetimes for Ag, Ta, and Pb. A method for obtaining the extrinsic positron lifetime components due to the radionuclide source is developed, and the experimentally determined source lifetime components are studied as a function of the sample atomic number. The Z dependence of the source foil component intensities were fitted using known expressions for positron backscatter and multiple scattering within the source sample geometry, neglecting backscatter from the foil. The foil material positron absorption coefficients were obtained and found to be comparable with the results of previous transmission experiments.

show abstract

“…A coecient of absorption and backscattering can be calculated based on several empirical formulae [49]. For example, in order to determine the backscatter coecient a formula developed by MacKenzie et al [4] can be used…”

Section: Multiple Scattering Modelmentioning

confidence: 99%

The Computer Code for Calculations of the Positron Distribution in a Layered Stack Systems

Siemek

Dryzek

2014

Acta Phys. Pol. A

View full text Add to dashboard Cite

In this paper we present experimental and theoretical studies of the implantation prole of positrons emitted from 22 Na radionuclide into layered sample. The measured prole for the nonsymmetrical, around the positron emitter, stack of aluminium and silver foils was measured using the depth scanning of implantation prole technique. For the description of the obtained results two theoretical approaches were applied. The rst one was the Monte Carlo simulation using the GEANT4 tool kit. The generated prole does not reproduce accurately the experimental prole. We proposed the multiple scattering model based on the fact that a positron due to backscattering can travel as an energetic particle several times through the whole sample before it annihilates. In this model absorption is also taken into account. The multiple scattering model algorithm was implemented in the LYS-1 program. The calculated prole using the LYS-1 program reproduces the experimental prole with much better accuracy.

show abstract

Positron Transmission and Scattering Measurements Using Superposition of Annihilation Line Shapes: Backscatter Coefficients

Cited by 59 publications

References 13 publications

Investigations of microstructures and defect structures in wear affected region created on Nimonic 80A during high temperature wear

Investigations of microstructures and defect structures in wear affected region created on Nimonic 80A during high temperature wear

Positron lifetimes of polycrystalline metals: A positron source correction study

The Computer Code for Calculations of the Positron Distribution in a Layered Stack Systems

Contact Info

Product

Resources

About