A continuous time-tagged positron beam and its application to materials research

P. Wesolowski, K. Maier, J. Major, A. Seeger, H. Stoll, T. Grund, M. Koch

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

A time-tagged relativistic positron beam with very low time jitter (≅ 80 ps with the present setup) has been installed at the Stuttgart pelletron accelerator. A position-sensitive ß+ detector with good angular resolution and small e+ directional straggling supplies the start signal for positron lifetime measurements. The stop signal of the positron lifetime spectrometer based on this "positron clock" is obtained in the conventional way from one of the annihilation γ quanta. Compared with the conventional γγ lifetime-measurement technique, this ß+γ lifetime spectrometer does not only give a substantially better time resolution but also, owing to the ß+ detector efficiency unity, a much higher coincidence count rate. This will permit routine age-momentum-correlation (AMOC) measurements, using the second annihilation photon. The positron clock can handle very high positron beam fluxes such as they will become available in e+ factories. In the Stuttgart setup we hope to reach, by using solid rare-gas moderators in the accelerator terminal, positron fluxes of about 106e+/s. A comparison between the moderation efficiencies of tungsten and rare-gas moderators under the vacuum conditions of the accelerator terminal is presented. AMOC measurements allow us to obtain time-resolved information on the evolution of the positron states (e.g., trapping of positrons at defects or positronium formation). As a surprising effect, "giant" Doppler broadening of the annihilation quanta of "young" positrons in diamond has been observed by means of a beam-based AMOC technique.

Original languageEnglish
Pages (from-to)468-473
Number of pages6
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume68
Issue number1-4
DOIs
Publication statusPublished - May 2 1992

Fingerprint

Positrons
positrons
Particle accelerators
Noble Gases
life (durability)
Momentum
moderators
accelerators
Moderators
Inert gases
momentum
clocks
Spectrometers
Clocks
rare gases
spectrometers
Fluxes
Detectors
Tungsten
Diamond

ASJC Scopus subject areas

  • Surfaces, Coatings and Films
  • Instrumentation
  • Surfaces and Interfaces

Cite this

A continuous time-tagged positron beam and its application to materials research. / Wesolowski, P.; Maier, K.; Major, J.; Seeger, A.; Stoll, H.; Grund, T.; Koch, M.

In: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, Vol. 68, No. 1-4, 02.05.1992, p. 468-473.

Research output: Contribution to journalArticle

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