MLZ is a cooperation between:

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich
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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 to determine 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 defect-concentration. In combination with a monoenergetic positron beam of variable energy depth-resolved defect analysis becomes possible.

Typical applications
  • Defect identification in thin layers and layered structures of semiconductors and insulators
  • Radiation induced defects in materials for fusion and fission reactors
  • Characterisation of free volumes in polymers and glasses
Technical Data

Beam properties

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

Sample

  • Limited to 5 × 5 mm2 – 9 × 9 mm2

Typical measurement times

  • < 10 min per spectrum (> 3·106 counts in the spectrum)
  • Depth-profile: 4 – 5 h (15 – 20 implantation energies, > 3·106 counts in the spectrum)
  • Time-window: 20 or 40 ns
  • Time-resolution: 260 – 280 ps
  • Peak/ background > 50000 : 1

Instrument Scientist

Dr. Werner Egger
Phone (office TUM): +49 (0)89 289-12299
Phone (office UniBW): +49 (0)89 6004-3507
E-Mail:

Operated by

UniBW

Instrument-DOI

doi:10.17815/jlsrf-1-52

Gallery

PLEPS
PLEPS
© W. Schürmann, TUM
Positron lifetime spectrum
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
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
PLEPS components

MLZ is a cooperation between:

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich