A concept of a scanning positron microscope

Uhlmann, K.; Triftshäuser, W.; Kögel, G.; Sperr, P.; Britton, D.T.; Zecca, Antonio; Brusa, R. S.; Karwasz, Grzegorz P.

doi:10.1007/bf00321331

Cited by 12 publications

(7 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This was, for example, the case of the Wayne State University (Detroit) experiment in its early version, using boron 11 B radioisotope what allowed to perform measurements of total cross sections in Ar [1] down to as little 0.4 eV while the measurements with a thick (ribbon) W moderator stopped at 4 eV [2]. Recently a new version of the tungsten moderator a thin 1 µm micro foil has been developed at Trento University [3][4][5][6], allowing measurements of total cross section down to a few tenths of eV.…”

Section: Introductionmentioning

confidence: 99%

Energy scale determination and energy resolution in positron total cross section measurements

Karwasz

Brusa

Pliszka

2010

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

We compare the recent values of positron total cross sections in benzene, cyclohexane and aniline by Zecca et al. with our previous measurements [Karwasz et al. Acta Phys. Pol. A, 107 (2005) 666] on the same apparatus. An apparent discrepancy disappears if Zecca's data are shifted by +0.2 eV; then their data can be approximated by the modified effective range theory, as well. This observation induced us to compare recent Trento data with other experiments and theories for polar targets, H 2 O and HCOOH. The evidence points out towards the need of a careful energy calibration in positron experiments.

show abstract

Section: Introductionmentioning

confidence: 99%

Energy scale determination and energy resolution in positron total cross section measurements

Karwasz

Brusa

Pliszka

2010

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

show abstract

“…In the EU framework, a worldwide unique scanning positron microscope has been constructed within the BRITE-Euram Programme jointly by München and Trento laboratories [40,41] and successfully applied to problems of fatigue and fracture in metals [42], but the technological impact of this project was limited, mainly because of the low positron intensities available with conventional laboratory positron sources, and therefore, it is currently set up at the NEPOMUC facility. Japanese positron beam in Tsukuba continues to challenge important questions, mainly in the fi eld of semiconductors [43].…”

Section: Toward a European Networkmentioning

confidence: 99%

Toward a European Network of Positron Laboratories

et al. 2015

View full text Add to dashboard Cite

Positron defectoscopyPositron annihilation is one of the few really nondestructive techniques in material science, giving unique information on types and concentrations of defects, even at a single parts per million (ppm) level, see, for example, [1]. Applications of positron annihilation techniques span from semiconductors [2,3] and metals [4] to polymers [5] and porous media [6]. In each case, answers given by positron methods are unique and complementary to other techniques.Two most common techniques, the analysis of Doppler broadening (DB) of the 511-keV annihilation line and the positron lifetime measurements, are to some extent complementary. The broadening brings information on momenta of electrons that positrons annihilate with. The main contribution to the annihilation comes from valence electrons, that is, possessing a few electron-volts energy. In the relativistic transformation, these energies translate to broadening of a few kiloelectron-volts, i.e. similar to the intrinsic resolution of gamma detectors used in experiments. Therefore, the information on relative contributions from valence and core (i.e., from defect sites) electrons is not straightforward. Somewhat phenomenological line-broadening parameters (central area S parameter, W lateral area, V 3 annihilation) are used, and some normalization is needed to make comparison between different experiments and theories. Evaluation of DB requires not only information of the overlap between a positron and electrons in the material but also a detailed

show abstract

“…26 Kögel et al focused the primary beam with a magnetic single pole lens placed behind a remoderator chamber, and ultimately achieved a φ2 μm beam with conventional SEM optics. 24,27 A reflectiontype remoderator, or W(100) single-crystal block, has been adopted in these systems, because a high-temperature anneal is easy to remove the defects and the impurities involved. However, the reflection geometry requires a complicated optics design, because the positron injection and reemission surfaces are the same.…”

Section: Positron Microbeam Formationmentioning

confidence: 99%

Analytical Methods Using a Positron Microprobe

2009

View full text Add to dashboard Cite

Positrons have been used for material analysis not only because of their novel characteristics, such as an ability to detect open-volume type defects in materials, but also because interactions with solids differ from those of electrons in such processes as scattering and diffraction. Monoenergetic positron beams and microbeams were developed in the 1980s, and positron experiments have made progress in material analyses. In this article we review the fundamental technique of microbeam fabrication, especially using a magnetically-guided positron beam, its extension to various analytical methods, and expectations for future research.

show abstract

A concept of a scanning positron microscope

Cited by 12 publications

References 7 publications

Energy scale determination and energy resolution in positron total cross section measurements

Energy scale determination and energy resolution in positron total cross section measurements

Toward a European Network of Positron Laboratories

Analytical Methods Using a Positron Microprobe

Contact Info

Product

Resources

About