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Digitale Medien

Irradiation-induced atomic defects in SiC studied by positron annihilation (1995)

Rempel, A. A. ; Schaefer, H. -E.

Springer

Applied physics 61 (1995), S. 51-53

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ISSN: 1432-0630

Schlagwort(e): 61.70 ; 61.80 ; 78.70

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau , Physik

Notizen: Abstract The present paper reports on positron lifetime measurements on atomic defects in SiC after low-temperature (80 K) electron irradiation of low (0.47 MeV) and high (2.5 MeV) electron energies and doses from 1.8×1017 to 1.9×1019 e/cm2 as well as after subsequent isochronal annealing up to 1900 K. For these studies the single crystals of nitrogen doped (2–3×1018 cm−3) SiC grown by a modified Lely technique with hexagonal structure (6H polytype) were used. According to the positron lifetime measurements, very different types of vacancy-like positron traps are introducted after irradiation with electrons of either low or high energy. The formation of defect agglomerates and their decay at high temperatures is studied during isochronal annealing and related to earlier studies.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01538210

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Digitale Medien

The positron beam at the stuttgart pelletron accelerator and its applications toβ +γ positron lifetime measurements (1987)

Bauer, W. ; Maier, K. ; Major, J. ; [weitere]

Springer

Applied physics 43 (1987), S. 261-267

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ISSN: 1432-0630

Schlagwort(e): 78.70 ; 61.70 ; 07.77

Quelle: Springer Online Journal Archives 1860-2000

Thema: Maschinenbau , Physik

Notizen: Abstract A slow-positron source has been installed in the therminal of an electrostatic 6.5 MeV accelerator and provides a monoenergetic positron beam in the few-MeV range. It will be used to operate a “fast” positron lifetime spectrometer based onβ + γ coincidences. The properties of the beam, the expected performance of the spectrometer, its advantages over conventionalγγ lifetime measurements, a number of intended applications, as well as recent positron-electron scattering experiments and plans for positron channelling and channelling-radiation studies are outlined.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00635181

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Digitale Medien

Evidence for a resonance in positron-electron scattering at 810 keV centre-of-mass Energy (1988)

Maier, K. ; Widmann, E. ; Bauer, W. ; [weitere]

Springer

The European physical journal 330 (1988), S. 173-181

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ISSN: 1434-601X

Schlagwort(e): 13.10.+q ; 12.20.Fv ; 14.80.Pb

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract A monoenergetic positron (e +) beam (ΔT/T〈5·10−4) from the Stuttgart pelletron accelerator and a 4.6 mg/cm2 Be target has been employed to investigatee + e −scattering in the MeV region in a large solid angle with high statistics by means of a novel positionsensitive detector system. Superimposed on the Bhabha scattering, a structure has been found at ane + kinetic energy of 2263 keV (810 keV excitation energy in thee + e −rest frame). From the energy-integrated resonance cross-section of $$\sigma _{res} \cdot \Gamma _{res}^{e^ + e^ - } $$ ≅30 b·eV (c.m.) and the standard resonance cross-section we estimate partial resonance widths $$\Gamma _{res}^{e^ + e^ - } $$ ≅72 meV or 24 meV for total angular momenta J=0 or J=1, respectively. The structure, which has not been predicted within the framework of quantum electrodynamics, coincides with one of the sum energies of the correlatede + e −lines observed in heavy-ion collisions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01293393

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