Experimental Setup for High-Resolution Positron Lifetime Spectroscopy

Bečvář, F.; Lešták, L.; Νovotný, I.; Procházka, I.; Šebesta, F.; Vrzal, J.

doi:10.4028/www.scientific.net/msf.175-178.947

Cited by 22 publications

(24 citation statements)

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“…[2]. The signal is taken from the 10th dynode and passed to a constant-fraction differential discriminator (CFDD) ORTEC Model 583.…”

Section: Methodsmentioning

confidence: 99%

“…The present FFS configuration was created by modification of our previous FS spectrometer [2]. Principal scheme of the FFS apparatus is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The energy (slow) signals are taken from the 9th dynode and shaped to resemble signal from a semiconductor detector [2]. The signals from both the detectors are led to a passive circuit (Σ) in which they are first properly balanced in order to compensate different gains of the start and stop PMT's and then summed.…”

Section: Methodsmentioning

confidence: 99%

“…Its detector part consists of two BaF 2 cylindrical scintillators (φ25 mm x 10 mm) coupled to Philips XP2020/Q photomultipliers (PMT's), see Ref. [2] for details. Screening of the PMT's from the environmental magnetic field is accomplished by means of a pair of the Helmholtz coils.…”

Section: Methodsmentioning

confidence: 99%

“…In our recent paper [2], a BaF 2 positron-lifetime spectrometer equipped with the FS scheme has been described. An excellent time resolution of ≈ 150 ps FWHM for a 22 Na positron source was attained with this spectrometer and kept during a long-time operation period.…”

Section: Introductionmentioning

confidence: 99%

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Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy

1999

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A BaF2 positron-lifetime spectrometer equipped with a coincidence system that represents a compromise between the traditional fast-fast and fast-slow arrangements is described. The main difference of the present configuration from both the fast-slow and fast-fast ones consists in use of a sum of the energy signals from the start and stop detectors to select the coincidence events. Quality of the spectrometer response function 150 ps FWHM for 22 Na) is very close to that observed for our fast-slow configuration with the equivalent detectors but throughput of the present apparatus is increased almost by a factor of two. Moreover, the electronic scheme becomes less complicated, which has also a positive impact on its cost.

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“…[2]. The signal is taken from the 10th dynode and passed to a constant-fraction differential discriminator (CFDD) ORTEC Model 583.…”

Section: Methodsmentioning

confidence: 99%

“…The present FFS configuration was created by modification of our previous FS spectrometer [2]. Principal scheme of the FFS apparatus is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy

1999

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Using of Modified Trapping Model in Positron-Lifetime Study of Cold-Worked Aluminium

Prochzka

Kmje

et al. 2000

phys. stat. sol. (a)

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Positron-lifetime (PL) and electrical resistivity studies of polycrystalline aluminium deformed by tensile stress at T 77 K were performed. It was found that the conventional trapping model (CTM) fails in interpretation of measured PL spectra due to strongly non-uniform spatial distribution of dislocations in the deformed samples. Therefore, a modified trapping model (MTM) was used in this study. Strongly non-uniform dislocation density was directly taken into account in the development of MTM. Comparison of the results obtained by MTM and CTM is given in the present work. Mean cell size in the deformed samples obtained from MTM analyses of PL spectra are compared with those measured by TEM. 440 J. C Ï i Âz Ïek et al. J. C Ï i Âz Ïek et al.

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Positron-Lifetime Investigation of Thermal Stability of Ultra-Fine Grained Nickel

Prochzka

Cieslar

et al. 2002

phys. stat. sol. (a)

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Thermal stability of ultra-fine grained (UFG) nickel (mean grain size 114 nm) prepared by high pressure torsion was studied by means of positron-lifetime spectroscopy (PLS) combined with TEM. The experimental results obtained by PLS are interpreted using the diffusion trapping model, which allows for determination of important physical parameters characterizing the specimens. The microstructure of the material studied is strongly inhomogeneous. The grain interiors with low dislocation density are separated by distorted regions with high numbers of dislocations. We have found that positrons are trapped at dislocations inside the distorted regions and in the microvoids situated inside the grains. Structure evolution with increasing temperature was studied in details using isochronal annealing of the specimen. We have found that recovery of the UFG structure involves the abnormal grain growth followed by further recrystallization in the whole volume of samples. It was shown that PLS is sensitive to structure changes, caused by the magnetostriction phenomenon.

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Experimental Setup for High-Resolution Positron Lifetime Spectroscopy

Cited by 22 publications

References 0 publications

Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy

Use of Energy Summing for Selection of Coincidence Events in Positron-Lifetime Spectroscopy

Using of Modified Trapping Model in Positron-Lifetime Study of Cold-Worked Aluminium

Positron-Lifetime Investigation of Thermal Stability of Ultra-Fine Grained Nickel

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