A positron annihilation lifetime measurement system with an intense positron microbeam

Oshima, Nobuyuki; Suzuki, Ryoichi; Ohdaira, Toshiyuki; Kinomura, A.; Narumi, T.; Uedono, Akira; Fujinami, Masanori

doi:10.1016/j.radphyschem.2009.06.035

Cited by 23 publications

(10 citation statements)

References 18 publications

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“…The beam is pulsed with a combination of two kinds of bunchers so that positron lifetime can be measured with a time resolution of less than ∼300 ps. A detailed description of the complex apparatus is given in ref . The beam spot size of the positron beam was below 600 μm for all the measurements in this study and was determined by scanning over a SiO 2 /stainless steel interface and calculating the balance point for each spectrum .…”

Section: Methodsmentioning

confidence: 99%

Free Volume Profiles at Polymer–Solid Interfaces Probed by Focused Slow Positron Beam

et al. 2015

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The properties of materials involving polymer−solid interfaces are determined not only by the properties of the constituents but also by the interfacial region of the polymer near the solid, the socalled interphase. Here we report on positron annihilation lifetime spectroscopy (PALS) measurements of the free volume near the interface with a focused positron beam. The measurements were performed at an interface between a Teflon AF 1600 film and a 30 nm thick SiN membrane from the backside of a Si substrate which was locally etched away to expose the ultrathin SiN membrane. We were able to focus the positron beam onto the exposed region and to probe the SiN−Teflon AF 1600 interfacial region with low implantation energies, resulting in very narrow implantation profiles and excellent depth resolution. We found a pronounced decrease in orthopositronium lifetime close the interface. On the basis of modeling, we could estimate the interphase width and the average density increase in the interfacial region as ∼12 nm and 5−7%, respectively.

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Section: Methodsmentioning

confidence: 99%

Free Volume Profiles at Polymer–Solid Interfaces Probed by Focused Slow Positron Beam

et al. 2015

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“…To overcome the problem of the requirement of the large sample size, we developed a positron probe microanalyzer using an electron linear accelerator at the National Institute of Advanced Industrial Science and Technology (AIST). [18][19][20][21] The positron probe microanalyzer is a positron lifetime measurement system, in which a pulsed, brightness enhanced positron beam 22 with a diameter much less than 1 mm is incident on the sample. With positron probe microanalysis (PPMA) it has become possible to perform PALS not only on samples of smaller size but also on a specified region or a point of particular interest on the sample of relatively large size.…”

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confidence: 99%

Free volume change of elongated polyethylene films studied using a positron probe microanalyzer

Oka

Oshima

Suzuki

et al. 2012

Applied Physics Letters

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Free volume change of low density polyethylene (LDPE) and high density polyethylene (HDPE) films upon mechanical deformation was microscopically investigated by positron probe microanalysis (PPMA). The ortho-positronium (o-Ps) lifetimes were gradually shortened by uniaxial deformation, indicative of shrinkage of the free volume. The o-Ps intensity for HDPE increased by deformation, whereas that for LDPE varied little. It suggests that destruction of crystallites plays an important role in the deformation of HDPE. PPMA is demonstrated to be a promising, powerful probe investigating free volume changes, at different local points subjected to different degrees of deformation, in elongated polymers.

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“…Besides imaging of the defect distribution in 2D (see e.g. [37][38][39][40]), 3D imaging was demonstrated on an irradiated quartz sample by Oshima et al [41] and further applied on ion irradiated alloys [42,43]. The NEutron induced POsitron source MUniCh (NEPOMUC) at the research neutron source Heinz Maier-Leibnitz (FRM II) of the Technical University of Munich provides a high intensity positron beam.…”

Section: Introductionmentioning

confidence: 99%

“…Besides imaging of the defect distribution in 2D (see e.g. [37][38][39][40]), 3D imaging was demonstrated on an irradiated quartz sample by Oshima et al [41] and further applied on ion irradiated alloys [42,43]. Due to the high intensity provided by the neutron induced positron source NEPOMUC spatially resolved DBS in combination with CDBS can be applied within short measurement times e.g.…”

Section: Introductionmentioning

confidence: 99%

Defect imaging and detection of precipitates using a new scanning positron microbeam

et al. 2017

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We report on a newly developed scanning positron microbeam based on threefold moderation of positrons provided by the high intensity positron source NEPOMUC. For brightness enhancement a remoderation unit with a 100 nm thin Ni(100) foil and 9.6% efficiency is applied to reduce the area of the beam spot by a factor of 60. In this way, defect spectroscopy is enabled with a lateral resolution of 33 μm over a large scanning range of 19×19 mm 2 . Moreover, 2D defect imaging using Doppler broadening spectroscopy (DBS) is demonstrated to be performed within exceptional short measurement times of less than two minutes for an area of 1×1 mm 2 (100×100 μm 2 ) with a resolution of 250 μm (50 μm). We studied the defect structure in laser beam welds of the high-strength age-hardened Al alloy (AlCu 6 Mn, EN AW-2219 T87) by applying (coincident) DBS with unprecedented spatial resolution. The visualization of the defect distribution revealed a sharp transition between the raw material and the welded zone as well as a very small heat affected zone. Vacancy-like defects and Cu rich precipitates are detected in the as-received material and, to a lesser extent, in the transition zone of the weld. Most notably, in the center of the weld vacancies without forming Cu-vacancy complexes, and the dissolution of the Cu atoms in the crystal lattice, i.e. formation of a supersaturated solution, could be clearly identified.

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A positron annihilation lifetime measurement system with an intense positron microbeam

Cited by 23 publications

References 18 publications

Free Volume Profiles at Polymer–Solid Interfaces Probed by Focused Slow Positron Beam

Free Volume Profiles at Polymer–Solid Interfaces Probed by Focused Slow Positron Beam

Free volume change of elongated polyethylene films studied using a positron probe microanalyzer

Defect imaging and detection of precipitates using a new scanning positron microbeam

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