Journal of large-scale research facilities, 1, A25 (2015) http://dx.doi.org/10.17815/jlsrf-1-52

Published: 19.08.2015

PLEPS: Pulsed low energy positron system

Heinz Maier-Leibnitz Zentrum
Universität der Bundeswehr München

Instrument Scientists:
- Werner Egger, LRT2, Universität der Bundeswehr München, Neubiberg, Germany,

phone: +49(0) 89 289 14609, email: werner.egger@unibw.de

Abstract: PLEPS, operated by the Universität der Bundeswehr München, located at NEPOMUC, is
a unique tool for depth pro�ling of defects with positron annihilation lifetime spectroscopy using a
pulsed positron beam of variable energy.

1 Introduction

Positron lifetime measurements allow to determine type and size of open volume defects (such as va-
cancies, vacancy-clusters, dislocations, grain boundaries etc., and free volumes in polymers) in a wide
variety of materials and provide information on defect-concentration. In combination with a monoen-
ergetic positron beam of variable energy depth-resolved defect analysis becomes possible.

2 Typical applications

• Defect identi�cation in thin layers and layered structures of semiconductors and insulators
• Radiation induced defects in materials for fusion and �ssion reactors
• Characterisation of free volumes in polymers and glasses

3 Technical Data

3.1 Beam properties

• Positron implantation energy: E = 0.5 – 20 keV
• Beam spot Ø ∼ 1 mm
• Count rate: ∼ 5000 – 10000 cps

1

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http://dx.doi.org/10.17815/jlsrf-1-52
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Journal of large-scale research facilities, 1, A25 (2015) http://dx.doi.org/10.17815/jlsrf-1-52

Figure 1: Instrument PLEPS at NEPOMUC (Copyright by W. Schürmann, TUM).

3.2 Sample

• Limited to 5 x 5 mm2 – 9 x 9 mm2

3.3 Typical measurement times

• < 10 min per spectrum
(> 3 · 106 counts in the spectrum)

• Depth-pro�le: 4 – 5 h
(15 – 20 implantation energies, > 3 · 106 counts in the spectrum)

• Time-window: 20 ns or 40 ns
• Time-resolution: 260 – 280 ps
• Peak/ background > 50000 : 1

2

http://dx.doi.org/10.17815/jlsrf-1-52
https://creativecommons.org/licenses/by/4.0/

	Introduction
	Typical applications
	Technical Data
	Beam properties
	Sample
	Typical measurement times