Unprecedented intensity of a low-energy positron beam

Hugenschmidt, C.; Löwe, Benjamin; Mayer, J.; Piochacz, C.; Pikart, Philip; Repper, R.; Stadlbauer, M.; Schreckenbach, K.

doi:10.1016/j.nima.2008.05.038

Cited by 96 publications

(61 citation statements)

References 13 publications

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“…30,31 The positron beam energy was varied between 1 to 18 keV, and each lifetime spectra contained >5 × 10 6 counts accumulated with a count rate of ∼6 × 10 3 s −1 . The instrument timing resolution function was normally described by three dominant, energydependent, terms; these showed a mean width, averaged over all energies, of 299 (20) ps.…”

Section: Methodsmentioning

confidence: 99%

Nonstoichiometry accommodation in SrTiO3thin films studied by positron annihilation and electron microscopy

et al. 2013

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Accommodation of nonstoichiometry in SrTiO 3 pulsed laser deposited (PLD) films was investigated using positron annihilation lifetime spectroscopy and (scanning) transmission electron microscopy. Increasing PLD laser fluence changed the stoichiometry from Ti to Sr deficient. Cation vacancy defects were detected, and the concentration ratio of Sr to Ti vacancies, [V Sr ]/[V Ti ], was observed to increase systematically in the Sr-deficient region, although no change in the electron microscopy lattice images was detected. Increasing Ti deficiency resulted in the accommodation of SrO layers in planar defects, and in the formation of vacancy cluster defects. A change from V Ti to V Sr defect positron trapping was also detected.

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Section: Methodsmentioning

confidence: 99%

Nonstoichiometry accommodation in SrTiO3thin films studied by positron annihilation and electron microscopy

et al. 2013

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“…A bright source of moderated positrons is already available [25] , and a promising positron accumulation trap concept, capable of holding more than 10 11 positrons, has been developed [26].…”

Section: Discussionmentioning

confidence: 99%

Pure electron plasmas confined for 90 ms in a stellarator without electron sources or internal objects

Brenner

Pedersen

2012

Physics of Plasmas

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We report on the creation and up to 90 millisecond sustainment of pure electron plasmas confined in a stellarator without internal objects. Injection of positrons into such plasmas are expected to lead to the creation of the first electron-positron plasma experiments. These newly created plasmas will also allow a study of pure electron plasmas without the perturbing presence of internal objects.The plasmas were created by thermionic emission of electrons from a heated, biased filament that was retracted in 20 milliseconds. The confinement of these transient plasmas is different from that of steady state plasmas with internal objects and emissive filaments, and is generally shorter, limited by ion buildup. The decay time is increased by lowering the neutral pressure, lowering the electron plasma temperature, or operating with neutrals with high ionization energies (helium). These findings are all consistent with ion accumulation being the cause for the shorter than expected confinement times. The magnetic field strength also moderately increases the decay times. The deleterious effect of ions is not expected to imply a similar deleterious effect when introducing positrons, but it implies that ion accumulation must be avoided also in an electronpositron experiment.

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“…The following experiments used the CDB spectrometer [14] at the high-intensity positron source NEPOMUC (NEutron induced POsitron source MUniCh) [15]. An average photon count rate of 32 000 counts s −1 was measured by each Ge-detectors with the beam diameter being set to 1.5 mm.…”

Section: (Coincident) Doppler Broadening Spectrometermentioning

confidence: 99%

Spatially resolved positron annihilation spectroscopy on friction stir weld induced defects

Hain

Hugenschmidt

Pikart

et al. 2010

Science and Technology of Advanced Materials

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A friction stir welded (FSW) Al alloy sample was investigated by Doppler broadening spectroscopy (DBS) of the positron annihilation line. The spatially resolved defect distribution showed that the material in the joint zone becomes completely annealed during the welding process at the shoulder of the FSW tool, whereas at the tip, annealing is prevailed by the deterioration of the material due to the tool movement. This might be responsible for the increased probability of cracking in the heat affected zone of friction stir welds. Examination of a material pairing of steel S235 and the Al alloy Silafont36 by coincident Doppler broadening spectroscopy (CDBS) indicates the formation of annealed steel clusters in the Al alloy component of the sample. The clear visibility of Fe in the CDB spectra is explained by the very efficient trapping at the interface between steel cluster and bulk.

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Unprecedented intensity of a low-energy positron beam

Cited by 96 publications

References 13 publications

Nonstoichiometry accommodation in SrTiO3thin films studied by positron annihilation and electron microscopy

Nonstoichiometry accommodation in SrTiO3thin films studied by positron annihilation and electron microscopy

Pure electron plasmas confined for 90 ms in a stellarator without electron sources or internal objects

Spatially resolved positron annihilation spectroscopy on friction stir weld induced defects

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