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A field-assisted moderator for low-energy positron beams (1987)

Beling, C. D. ; Simpson, R. I. ; Charlton, M. ; [et al.]

Springer

Applied physics 42 (1987), S. 111-116

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ISSN: 1432-0630

Keywords: 78.70 ; 72.90 ; 79.90

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract A new positron field-assisted (FA) moderator based on the drift of positrons across a cooled silicon crystal is proposed. Using estimates for both theβ + implantation profile and attainable drift velocities, the efficiency of drift to a slow e+ emitting surface is calculated using a diffusion equation which incorporates terms describing positron drift and annihilation. It is conjectured that efficiencies of up to 10% can be achieved. The use of epitaxially grown metallic suicide contacts to facilitate the application of the electric field is described and the consequences of using such contacts are fully discussed. Applications of the FA transmission mode moderator described here to produce timed brightness enhanced beams are briefly discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00616719

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Influence of formulation chemistry on the locus of failure of adhesive joints (1995)

Taylor, A. M. ; McLean, C. H. ; Charlton, M. ; [et al.]

Chichester [u.a.] : Wiley-Blackwell

Surface and Interface Analysis 23 (1995), S. 342-348

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ISSN: 0142-2421

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Physics

Notes: The durability of photocured resins adhered to ceramic substrates has been investigated. Monochromated XPS and time-of-flight SIMS were employed to determine the precise locus of failure in butt-joints comprised of a photocured resin adhered to either a 96% pure, debased alumina substrate or single-crystal silicon. Prolonged (〉 14 days) immersion in water at 50°C resulted in cohesive failure, with 1-2 nm of polymer remaining on one of the ceramic substrates. An absence in the spectrum of any components attributable to characteristic groups from a major constituent of the polymer within this overlayer suggested the possibility that one of the minor resin components was aggregating at the organic/inorganic interface to produce an in situ weak boundary layer. The interactions of some of the organic molecules present in the formulation with the α-alumina substrate were investigated using molecular modelling techniques to indicate the most favourable interactions with the substrate. Durability studies were also carried out on a reformulated photocured resin to investigate the effect of removal of the ethoxylated methacrylate monomer, suspected of being the principal organic component at the weak boundary layer, on both joint performance and locus of failure.

Additional Material: 7 Ill.