Investigations of HAVAR® Alloy Using Positrons

2012 ◽  
Vol 331 ◽  
pp. 95-112 ◽  
Author(s):  
S. May Tal Beck ◽  
Wolfgang Anwand ◽  
Andreas Wagner ◽  
Gerhard Brauer ◽  
A. Beck ◽  
...  
Keyword(s):  
Lattice Structure ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Total Charge ◽  
Slow Positron ◽  
Positron Spectroscopy ◽  
Thin Foils ◽  
Transmission Electron ◽  
Cold Rolled ◽  
Proton Dose

A study of irradiation-induced damage in HAVAR® foils was initiated in order to extract the highest proton dose the foils can sustain. The lattice structure of HAVAR® foils in different metallurgic conditions is presented, as well as visible internal structure, measured by Transmission Electron Microscopy (TEM). Positron Annihilation Spectroscopy (PAS) techniques were used to investigate these foils, and another foil that had been irradiated to the maximal proton dose limit, set by the manufacturer to a total charge of 1 mAh (= 3.6 C). PAS techniques included Doppler broadening (DB) measurement in the SPONSOR beam and lifetime (LT) measurements, both carried at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Both positron spectroscopy methods show clear differences between the investigated foils, with distinguished characteristics for annealed, cold-rolled and irradiated foils. The advantages of using a slow positron beam to study thin foils and defect profiles, over a table-top LT spectrometer, are discussed and demonstrated by the HAVAR® measurements.

Positron spectroscopy of bulk and near-surface defects in semiconductors

1989 ◽  
Vol 67 (8) ◽  
pp. 813-817
Author(s):  
P. Hautojārvi
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Surface Defects ◽  
Positron Beam ◽  
Near Surface ◽  
Slow Positron ◽  
Positron Spectroscopy ◽  
Positron Lifetime Spectroscopy ◽  
Defects In Semiconductors ◽  
Ion Implanted

The use of positron annihilation to study defects in semiconductors is discussed. Positron-lifetime spectroscopy reveals As vacancies in as-grown GaAs and gives information on ionization levels. The vacancy profiles in ion-implanted Si are investigated by slow positron beam.

scholarly journals Future of Positron Spectroscopy and Slow Positron Beam.

Materia Japan ◽  
1996 ◽  
Vol 35 (2) ◽  
pp. 165-173
Author(s):  
Shoichiro Tanigawa
Keyword(s):  
Positron Beam ◽  
Slow Positron ◽  
Positron Spectroscopy

On the disappearance of fine, disc-like features from thin foils of steel

1991 ◽  
Vol 49 ◽  
pp. 608-609
Author(s):  
S. W. Thompson
Keyword(s):  
Room Temperature ◽  
Sheet Steel ◽  
Rolled Sheet ◽  
Steel Company ◽  
Thin Foils ◽  
Transmission Electron ◽  
Fine Carbide ◽  
Iced Water ◽  
Cold Rolled ◽  
Carbide Particles

Fine carbide particles form in quenched-and-aged specimens of iron containing a small amount of carbon. Similar precipitation occurs in ferrite grains within dual-phase steels. The particles have been described as discs or loops, typically about 20 run in diameter and 2 nm thick, which lie on ﹛100﹜ planes within ferrite grains. The precipitates are believed to form in association with vacancies and produce increases in hardness and yield strength. Two studies showed that these features disappeared after heating specimens in the transmission electron microscope (TEM), and this note reports further on this phenomenon.Continuously annealed and cold-rolled sheet steel (provided by Inland Steel Company) contained (in wt pet) 0.087 C, 0.97 Mn, 0.27 Si, 0.034 Al, 0.008 S, and 0.005 N. Specimens were intercritically annealed at 770°C for five minutes and quenched in iced water. Tensile testing was conducted within one day of heat treatment, and then specimens were stored at room temperature for about six months. Thin foils were produced by conventional thinning methods and jet polished at 75 V and 80 mA in an electrolyte containing 95% acetic acid and 5% perchloric acid. Specimens were examined in a Philips EM400 operated at 120 kV.

scholarly journals Development of Positron Microbeam in AIST

2008 ◽  
Vol 607 ◽  
pp. 238-242 ◽  
Author(s):  
Nagayasu Oshima ◽  
Ryoichi Suzuki ◽  
Toshiyuki Ohdaira ◽  
Atsushi Kinomura ◽  
T. Narumi ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Spatial Resolution ◽  
Transport System ◽  
Linear Accelerator ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Beam Size ◽  
Electron Linear Accelerator ◽  
Slow Positron ◽  
Magnetic Transport

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.

Observations of the Cell Structure of Heavily Rolled Phosphor Bronze

1973 ◽  
Vol 31 ◽  
pp. 162-163
Author(s):  
R. N. Caron ◽  
S. Shapiro
Keyword(s):  
Cell Structure ◽  
Rolling Plane ◽  
Average Thickness ◽  
Rolled Sample ◽  
Final Thickness ◽  
Standard Methods ◽  
Thin Foils ◽  
Transmission Electron ◽  
Cold Rolled ◽  
Cold Worked

Transmission electron microscopy has often been used to observe the nature of the heavily cold worked condition in metals in order to evaluate the effect of this microstructure on subsequent processes and properties. However, interpretation of a heavily cold rolled microstructure when viewed normal to the rolling plane is made difficult by the fact that the average thickness of the elongated cells resulting from such deformation is often smaller than the thickness of the foil. The final thickness of a heavily rolled structure is often too thin for convenience in making thin foils trans- verse to the rolline plane. The technique of plating copper to thicken the thin cold rolled sample sufficiently for om pat ibility with standard methods for preparing transmission foils has been successfully used.

Diffusion Processes in the Sintering of Zirconia-Based Nanomaterials

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.

scholarly journals Slow positron beam at the JINR, Dubna

Nukleonika ◽  
2015 ◽  
Vol 60 (4) ◽  
pp. 725-728 ◽  
Author(s):  
Paweł Horodek ◽  
Andrey G. Kobets ◽  
Igor N. Meshkov ◽  
Alexey A. Sidorin ◽  
Oleg S. Orlov
Keyword(s):  
Diffusion Length ◽  
Nuclear Research ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Low Energy ◽  
Positron Energy ◽  
Slow Positron ◽  
Tungsten Foil ◽  
Sample Chamber ◽  
Variable Energy

Abstract The Low Energy Positron Toroidal Accumulator (LEPTA) at the Joint Institute for Nuclear Research (JINR) proposed for generation of positronium in flight has been adopted for positron annihilation spectroscopy (PAS). The positron injector generates continuous slow positron beam with positron energy range between 50 eV and 35 keV. The radioactive 22Na isotope is used. In distinction to popular tungsten foil, here the solid neon is used as moderator. It allows to obtain the beam intensity of about 105 e+/s width energy spectrum characterized by full width at half maximum (FWHM) of 3.4 eV and a tail to lower energies of about 30 eV. The paper covers the characteristic of variable energy positron beam at the LEPTA facility: parameters, the rule of moderation, scheme of injector, and transportation of positrons into the sample chamber. Recent status of the project and its development in the field of PAS is discussed. As an example, the measurement of the positron diffusion length in pure iron is demonstrated.

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

2012 ◽  
Vol 331 ◽  
pp. 25-40 ◽  
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.

The spin polarized slow positron beam and the reemitted polarized slow positron spectroscopy

1997 ◽  
Vol 116 ◽  
pp. 168-176 ◽  
Author(s):  
Terunobu Nakajyo ◽  
Mutsumi Tashiro ◽  
Tomoya Koizumi ◽  
Ikuzo Kanazawa ◽  
Fumio Komori ◽  
...  
Keyword(s):  
Positron Beam ◽  
Slow Positron ◽  
Positron Spectroscopy ◽  
Spin Polarized

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

Metals ◽  
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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