Development of Positron Microbeam in AIST

To improve the spatial resolution of positron annihilation spectroscopy (PAS), a system to produce an intense positron microbeam was developed in AIST. A slow positron beam, which was produced by an electron linear accelerator, was focused by a lens onto a remoderator to enhance its brightness. The brightness-enhanced beam with an intensity of ≈1 × 106 e+/s was extracted from the remoderator and focused onto the sample by a lens. The beam size at the sample was 25 μm, which is more than two and half orders of magnitude smaller than that in the magnetic transport system (≈10 mm). Hence, the spatial resolution of PAS with an AIST positron microbeam can be drastically improved relative to PAS using conventional methods.

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Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.331.41 ◽

2012 ◽

Vol 331 ◽

pp. 41-52 ◽

Cited By ~ 3

Author(s):

Andreas Wagner ◽

Wolfgang Anwand ◽

Maik Butterling ◽

Thomas E. Cowan ◽

Fine Fiedler ◽

...

Keyword(s):

Positron Annihilation ◽

Linear Accelerator ◽

Electron Accelerator ◽

Positron Annihilation Spectroscopy ◽

Doppler Broadening ◽

Electron Linear Accelerator ◽

Positron Annihilation Lifetime ◽

Electron Bremsstrahlung ◽

New Type ◽

Set Up

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

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Diffusion Processes in the Sintering of Zirconia-Based Nanomaterials

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.26.25 ◽

2013 ◽

Vol 26 ◽

pp. 25-31

Author(s):

Oksana Melikhova ◽

Jakub Čížek ◽

Ivan Procházka ◽

Wolfgang Anwand ◽

Tetyana E. Konstantinova ◽

...

Keyword(s):

Positron Annihilation ◽

Elevated Temperatures ◽

Diffusion Processes ◽

High Sensitivity ◽

Positron Beam ◽

Positron Annihilation Spectroscopy ◽

Atomic Scale ◽

Slow Positron ◽

Co Precipitation ◽

Non Destructive

In the present work, zirconia-based nanomaterials with various stabilizers were prepared by a co-precipitation technique. Defects in these nanomaterials were characterized by positron annihilation spectroscopy which is a non-destructive technique with a high sensitivity to open volume defects and atomic scale resolution. It was found that zirconia-based nanomaterials contain vacancies and also nanoscale and meso-scale pores. Diffusion processes which occur in the nanomaterials sintered at elevated temperatures were investigated by depth sensitive positron annihilation studies on a variable energy slow positron beam. It was found that sintering causes intensive grain growth and residual porosity is removed from samples by diffusion to the surface.

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Design and Construction of a Slow Positron Beam for Solid and Surface Investigations

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.331.25 ◽

2012 ◽

Vol 331 ◽

pp. 25-40 ◽

Cited By ~ 52

Author(s):

Wolfgang Anwand ◽

Gerhard Brauer ◽

Maik Butterling ◽

Hans Rainer Kissener ◽

Andreas Wagner

Keyword(s):

Positron Beam ◽

Positron Annihilation Spectroscopy ◽

Vacuum System ◽

Sample Holder ◽

Slow Positron ◽

Financial Costs ◽

Sample Chamber ◽

Magnetic Transport ◽

Short Time ◽

Design And Construction

On the basis of the design and construction of the slow positron beam SPONSOR at the Helmholtz-Centre Dresden-Rossendorf an example is given how to build-up a simple slow positron beam for solid surface investigations within a short time and without high financial costs. The system uses a 22Na source and consists of three main parts: (1) the source chamber with a thin film tungsten moderator used in transmission, and a pre-accelerator stage, (2) the vacuum system with magnetic transport, a bent tube for energy selection and an accelerator, (3) the sample chamber with a sample holder, Ge detectors and (4) facilities for remote control and data acquisition. These parts are described in detail. The paper is preferentially addressed to beginners in the field of slow positron beam techniques and other readers being generally interested in positron annihilation spectroscopy.

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On the Limitations of Positron Annihilation Spectroscopy in the Investigation of Ion-Implanted FeCr Samples

Metals ◽

10.3390/met11111689 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1689

Author(s):

Vladimir Slugen ◽

Jarmila Degmova ◽

Stanislav Sojak ◽

Martin Petriska ◽

Pavol Noga ◽

...

Keyword(s):

Ion Implantation ◽

Positron Annihilation ◽

Neutron Irradiation ◽

Surface Region ◽

Positron Beam ◽

Positron Annihilation Spectroscopy ◽

Radiation Embrittlement ◽

Nuclear Facilities ◽

Near Surface ◽

Slow Positron

New materials for advanced fission/fusion nuclear facilities must inevitably demonstrate resistance to radiation embrittlement. Thermal and radiation ageing accompanied by stress corrosion cracking are dominant effects that limit the operational condition and safe lifetime of the newest nuclear facilities. To study these phenomena and improve the current understanding of various aspects of radiation embrittlement, ion bombardment experiments are widely used as a surrogate for neutron irradiation. While avoiding the induced activity, typical for neutron-irradiated samples, is a clear benefit of the ion implantation, the shallow near-surface region of the modified materials may be a complication to the post-irradiation examination (PIE). However, microstructural defects induced by ion implantation can be effectively investigated using various spectroscopic techniques, including slow-positron beam spectroscopy. This method, typically represented by techniques of positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy, enables a unique depth-profile characterisation of the near-surface region affected by ion bombardment or corrosion degradation. One of the best slow-positron beam facilities is available at the pulsed low-energy positron system (PLEPS), operated at FRM-II reactor in Munich (Germany). Bulk studies (such as high energy ion implantation or neutron irradiation experiments) can be, on the other hand, effectively performed using radioisotope positron sources. In this paper, we outline some basics of the two approaches and provide some recommendations to improve the validity of the positron annihilation spectroscopy (PAS) data obtained on ion-irradiated samples using a conventional 22Na positron source.

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Positron Annihilation Spectroscopy at LEPTA Facility

Materials Science Forum ◽

10.4028/www.scientific.net/msf.733.322 ◽

2012 ◽

Vol 733 ◽

pp. 322-325 ◽

Cited By ~ 4

Author(s):

Aleksey A. Sidorin ◽

Igor Meshkov ◽

E. Ahmanova ◽

M. Eseev ◽

A. Kobets ◽

...

Keyword(s):

Positron Annihilation ◽

Condensed Matter ◽

Positron Beam ◽

Positron Annihilation Spectroscopy ◽

Layered Structures ◽

Low Energy ◽

Slow Positron ◽

Monochromatic Beam

The Low Energy Positron Toroidal Accumulator (LEPTA) at JINR proposed for generation of positronium in flight can be used for positron annihilation spectroscopy (PAS) [1]. The positron injector of the LEPTA facility can generate continuous a slow positron beam with the intensity up to 1∙107s-1 at the energy in the range of a few eV to 100 keV and width of the spectrum 1 – 2 eV. The injector is based on radioactive 22Na isotope. The solid neon is used as a moderator to generate monochromatic beam. The parameters of the positron beam allow scanning the condensed matter in depth up to 10 microns with resolutions less than 10 nanometers and investigating layered structures for microelectronics and properties of a surface.

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