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MLZ (eng)

Lichtenbergstr.1
85748 Garching

PLEPS

Pulsed low-energy positron system

PLEPS is a unique tool for depth profiling of defects with positron annihilation lifetime spectroscopy using a pulsed positron beam of variable energy.

Positron lifetime measurements allow the determination of the type and size of open volume defects (such as vacancies, vacancy-clusters, dislocations, grain boundaries etc., and free volumes in polymers) in a wide variety of materials and provide information on the defect concentration. Combined with a monoenergetic positron beam of variable energy, depth-resolved defect analysis becomes possible. [1]

[1] Egger, W., J. Phys. Conf. Ser. 240(1), 012164 (2010).

Typical applications

Defect identification in thin layers and layered structures of metals, semiconductors and insulators
Radiation-induced defects in materials for fusion and fission reactors
Characterisation of free volumes in polymers and glasses and membranes

Technical data

Beam properties

Positron implantation energy: 0.5 – 20 keV
Beam spot: Ø < 1 mm
Count rate: ~ 10 000 – 20 000 cps

Sample

Limited to 3 × 3 – 10 × 10 mm²

Typical measurement times

~ 4 – 10 min per spectrum (4 × 10⁶ counts in the spectrum)
Depth profile: 1 – 2 h (15 – 20 implantation energies, 4 × 10⁶ counts in the spectrum)
Time window: 40 ns / 160 ns / 320 ns
Time resolution: 180 ps
Peak/ background: > 100 000 : 1

Instrument scientist

Dr. Werner Egger
Phone (office MLZ): +49 (0)89 289-14609
Phone (office UniBw): +49 (0)89 6004-3507
E-mail: werner.egger@unibw.de

Operated by

Funding

Citation templates for users

In all publications based on experiments on this instrument, you must provide some acknowledgements. To make your work easier, we have prepared all the necessary templates for you on this page.

Gallery

PLEPS

Positron lifetime spectrum

Typical positron lifetime spectrum in an epoxy-based industrial adhesive. The positron implantation energy was 18 keV according to a mean implantation depth of 4 µm. The spectrum can be decomposed into three exponentials with three different lifetimes. From the longest lifetime of 2.3 ns the mean size of free volume cavities in the polymer is estimated to be 0.13 nm3.

AMoC spectrum

Age-Momentum Correlated (AMoC) spectrum in Kapton measured with a BaF2 scintillation detector and a HP-Ge detector in coincidence. AMoC measurements contain information about the type of defect and its chemical environment, thus giving a more complete picture of the annihilation site than lifetime measurements and Doppler broadening measurements alone.

PLEPS components